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FUR DYEING AND FUR DRESSING

PRINCIPLES AND PRACTICE
OF
FUR DRESSING AND FUR DYEING

BY
WILLIAM E. AUSTIN, B.S.
CONSULTING CHEMIST TO THE FUR INDUSTRY

ILLUSTRATED

Copyright, 1922, by
D. VAN NOSTRAND COMPANY

All rights reserved, including that of translation into foreign languages, including the Scandinavian

PRINTED IN THE UNITED STATES OF AMERICA

PREFACE

The great increase in the use of furs during the past few decades has caused the fur dressing and dyeing industry to rise from relative insignificance to considerable importance as a branch of applied chemistry. The past eight years, moreover, have witnessed the virtual transference of the leadership in the dressing and dyeing of furs from Europe to America, and in the quality and variety of products, the domestic industry is now in every way the equal of, and in many respects superior to the foreign. The great bulk of American furs which formerly were sent to Leipzig, Paris or London to be dressed and dyed, are now being dressed and dyed in this country.

In spite of these facts, very little is generally known about the nature and manner of the work constituting the dressing and dyeing of furs. Even among members of other branches of the fur trade, there is very little accurate information on the subject. Real knowledge concerning fur dressing and dyeing is possessed only by those actually engaged in the industry. The interest and efforts of scientists and technologists have been enlisted to only a small extent in the technical development of the industry. The reason for this may be attributed to two related causes: first, the almost monastic seclusion in which fur dressers and dyers, particularly the latter, conducted their operations, and even to-day the heavy cloud of mystery is being dispelled but very slowly; and second, as a consequence of the first, the lack of any reliable literature on the subject. Of the few books which have been written on the industry of fur dressing and fur dyeing (all of them either German or French), most are hopelessly out of date, or contain no trustworthy data; or, if they do have real merit, they cannot be obtained. Numerous articles in the technical journals are of interest, but they contain very little information of value.

This work is intended for a two-fold purpose: first, that it may serve as a text-book for those who expect to make fur dressing and dyeing their vocation. The fundamental principles upon which the industry is based are discussed in the light of the most recent chemical and technical developments, and the most important operations are treated fully and systematically, and are illustrated with practical examples.

Secondly, as a practical handbook for the worker in the fur dressing and dyeing plant. The latest factory processes and methods are described, and numerous working formulas given. The formulas are all such as have been successfully used on a large scale, and give satisfactory results when applied under the proper conditions.

In addition, it is believed that the book will prove of interest to chemists and other students of industrial chemistry, since it will be an introduction into a field of applied chemistry, about which very little is known to those outside of the industry.

Thanks are due to Dr. L. A. Hausman, of Cornell University, for material used in Chapter II; to Dr. E. Lesser of the American Dyewood Company, for information and assistance on the subject of Vegetable Dyes; to the Gaskill Chemical Corp., American Aniline Products, Inc., the Cassella Company, and the Franklin Import & Export Co., for information about their products in connection with the chapter on Oxidation Colors; to F. Blattner, Fletcher Works, Inc., S. M. Jacoby Co., Proctor & Schwartz, Inc., Reliable Machine Works, Seneca Machine & Tool Co., Inc., and the Turner Tanning Machinery Co., for the use of the cuts of the various machines.

William E. Austin.

New York, May, 1922.

TABLE OF CONTENTS

FUR DRESSING AND FUR DYEING

CHAPTER I
FURS AND THEIR CHARACTERISTICS

Furs have in general two uses: as the goods which constitute the basis of the furrier’s art, and as the source of material for the hat manufacturer. In the latter case, only the hair part of the fur is utilized in the hat trade for the production of felt, the skin being either made into leather, or used as the raw material for making high-grade glue and gelatine. It is the furrier, therefore, who uses the great bulk of furs, and requires them to be dressed and dyed.

In discussing the dressing and the dyeing of furs, there are, broadly speaking, two fundamental subjects to be considered: first, the raw materials employed, which are, of course, the skins or pelts as they come from the trapper. (Other substances used in fur dressing and dyeing are accessories, and will be studied in connection with the processes.) Second, all those operations, physical and chemical, manual and mechanical, to which the raw skins have to be subjected in order to obtain the finished fur, ready for use by the furrier.

Next to the inherent qualities of the fur skin, the future value of a fur in a manufactured garment depends largely on the dressing and dyeing it receives. It is in these operations that the beauty of the fur can be brought out to its fullest degree, and if possible, enhanced, or the attractive features can be marred or destroyed, and the fur rendered quite worthless. Therefore, it is quite essential for the fur dresser and the fur dyer in addition to the technical knowledge and experience which are the fundamental requisites of the industry, also to have more than a superficial familiarity with the various kinds of furs. In fact, an accurate knowledge of the nature and chief characteristics of furs in general, and of the individual classes, in particular, is almost indispensable to obtain the best results. The habits and habitats of the various fur-bearing animals are factors which largely determine the constitution of the fur, and the nature of the skin. There are as many different kinds of fur hair, with as many different kinds of skin bearing the hair, as there are classes of furs. The methods of dressing, and often, if the furs are to be dyed, the manner of dyeing, are determined by the nature of these component parts of furs. Various chemicals affect furs in widely different ways. The divergence with regard to the physical and chemical properties of the classes of furs is such as to make almost imperative a detailed knowledge of the typical members of the many groups of commercial furs.

To be sure, there are many engaged in the dressing and dyeing of furs, who never made a formal study of this phase of the industry, but acquired their knowledge empirically, and are apparently quite successful. It must not be denied, that practise and experience, as in every field of enterprise, are essential to obtaining the best results. But the time and cost of acquiring this precious experience can be considerably reduced by systematically studying the important characteristics and properties of furs. These will be treated briefly, but in sufficient detail to form a basis for discussing the operations of dressing and dyeing.

Fur-bearing animals are mammals whose skins are used in the manufacture of fur garments and other fur wearing apparel. The skin, when it is removed from the animal is called a pelt, or sometimes, in the case of large animals, a hide. The pelt, after having been dressed and dyed, is called a fur, the skin part being referred to as the leather, and the hair as the pelage. However, this terminology is not strictly adhered to in practise, and the various terms are often employed interchangeably.

The various fur-bearing animals differ considerably in the characteristics of the furs they yield. With few exceptions, notably beaver and Alaska red fox, the depth of shade increases as the habitat of the animal species is nearer the equatorial regions. There seems to be a direct relationship between the intensity of color of the pelt, and the distance from, or proximity to the polar, or the torrid regions. Thus, white mammals, such as polar bear, ermine, white or Siberian hare, are found only in the northern lands. An exception is the sheep, which, due to its domestic nature, can be found in almost all parts of the civilized world. Tropical animals on transportation to colder climates, have been known to become lighter-haired when adapted to their new environment. The skins of animals living in dense woods or forests, are generally of a deeper color than in animals living in more open territory. As a general rule, fur-bearing animals have darker hair on the back than on the sides and belly. The badger, hamster, ratel and panda are exceptions having the darker hair on the belly and sides, and the lighter hair on the back. With regard to the intensity of color, the skunk has the blackest fur, although some domestic cats are also quite black. Other animals whose fur is nearly black, are the black bear, and the black fox, which is a variety of the silver fox, but the color is often of a brownish shade. The colors which predominate among animals of the fur-bearing variety, are white, black, brown, and grey. Less common are yellow shades, and those known as blue.

The quality of the fur on all mammals improves with cold, and animals living at greater altitudes, with correspondingly lower temperatures, have thicker and finer hair than those living nearer sea-level. A cold winter generally produces fur of high quality and fine color, a mild winter may cause the hair to be inferior. In all climates, animals found in dense woods, have fur which is deeper, silkier, thicker, and glossier than that of animals living in the open. Animals inhabiting inland lakes and rivers, have finer and softer hair than those living near the coast or land exposed to sea winds. In general, the hair of animals of the cold regions is short, fine, soft, and downy, while the hair of animals of warmer lands, is longer, stiffer, and harder.

Both the quality and color of the fur vary with the age of the animal. The young usually have a thicker coat of fur than adults, but the hair is too soft, and the skin generally too tender to be fit for use. In certain cases, particularly the baby lambs, very young skins are especially prized, and eagerly sought, but extraordinary care has to be exercised in working with them. Fur is at its best when the animal is between one and two years old. After this age, the fur becomes coarse and scraggy. The animal attains its fullest growth of hair usually in the height of winter, and the fur is best between then and very early spring. Before mid-winter the hair is short and thin, and in the spring it begins to shed, and will continue to fall out even in the dressed fur. The color of the hair also becomes lighter with age, and the new growth which generally comes in the fall is darker than the old coat.

Different members of the same species, will, other factors such as age and season being equal, vary as to color and quality. There may even be several different color phases of the same species of animal, such as the cross fox and the silver fox, both of which are of the same genus as the red fox; black muskrats are of the same class as the brown variety, etc. The individual pelt likewise presents many variations in color and nature of the hair. In some parts, the hair is thicker and softer than others, and the color varies in intensity and shade throughout the different sections of the skin.

Furs do not have differences confined to the hair part only; the leather also presents considerable variation among the different fur-bearing animals, especially in regard to the weight and thickness. The durability of furs, relatively considered under similar conditions of wear, also varies widely. In the following table the relative durability of dressed furs, and in certain instances also dyed furs, otter being taken as standard, is given, as well as the weight in ounces per square foot of skin of these furs.

In estimating the value of a fur, many factors have to be considered. There is no one standard by which the skins are judged, each kind of fur having its own criterion. However, the general points by which raw furs are graded are, color, size, origin, quality and quantity of hair, condition of leather, date or season of trapping, methods of handling, etc. Beaver, for example, is graded as large, medium, small and cubs. Red foxes, first, into Alaska, Labrador, and Nova Scotia, and then these divisions are classed as large, medium and small. Skunks are graded according to the amount of white on the skin, the less white, the more valuable the fur.

The qualities which make a fur desired depend first of all on the nature of the fur itself. Pretty color, luster, thickness, softness, length, uniformity and regular fall of the hair are the chief points to be considered. While the leather part of the fur is of secondary importance in the evaluation of a fur, it must possess strength, lightness of weight, and when properly dressed, should be supple and have a certain firmness or ‘feel.’ The abundance or scarcity of a fur-bearing animal also determines the value of the fur. Furs which are always comparatively rare, such as silver fox, Russian sable, chinchilla, etc., are always highly prized. In this connection, circumstances which tend to decrease the number of available pelts of any particular animal, such as pestilences, gradual extermination due to excessive trapping, prevention of trapping, by protective laws, also affect the value of a fur. A third factor which has an influence on the value of furs, is the prevailing style or fashion. Many kinds of furs which are both beautiful and rare, such as Russian sable or chinchilla, are practically unaffected by the whims of fashion. But a fur of ordinary value may at times become so popular, that the demand for it will cause its price to be greatly increased. Similarly, a fur which has enjoyed a considerable vogue, may pass out of demand for a time and consequently depreciate in value.

A detailed description of the various furs used in commerce is not within the scope of this work, because such an account rightly belongs in a book on zoölogy. However, it is desirable that the reader who is interested in the dressing and dyeing of furs should have at least a passing acquaintance with the chief furs used in commerce, together with such of their individual characteristics as are of importance. The figures given are for the average dressed skin.[1]

Astrachan, see Lambs.

Badger.—2 × 1 ft. This is one of the few animals whose fur is darker on the belly than on the back. The American sorts have coarse, thick under-hair of a pale fawn or stone color, with a growth of longer black and white hairs 3–4 inches long. The Japanese varieties are usually dyed for imitation skunk. The American kind is also dyed occasionally but is mostly used natural. Badger hair is very extensively used for ‘pointing.’

Bear, Black.—6 × 3 ft. Has fine, dark brown under-hair, with bright, flowing black top-hair 4 inches long. The fur of cubs is nearly as long, although the skins are much smaller, and the hair is finer, softer, and lighter-pelted. The best skins are from Canada.

Bear, Brown.—6 × 3 ft. Similar to the Black Bear, but more limited in number. The color ranges from a light yellow to a rich dark brown. The best and most valuable sorts come from the Hudson Bay territory, inferior skins coming from Europe and Asia.

Bear, White.—10 × 5 ft. This is the largest of the bears. The hair is short and close except on the flanks, while the color ranges from white to yellow. The best skins come from Greenland, the whitest being the most valuable.

Beaver.—3 × 2 ft. This is the largest of the rodents, and is very widely used; formerly to a great extent in the hat trade. The under-hair is close and of a bluish-brown hue, and nearly an inch deep. The over-hair is coarse, bright black or reddish-brown in color, and is usually plucked out, as the under-hair is the attractive part of the fur. The darkest skins are the most valuable. Formerly beaver was used to dye in imitation of seal, but more suitable furs are now used.

Broadtail, see Lambs.

Caracul, see Lambs.

Cat, Civet.—9 × 4¹⁄₂ inches, with short, thick and dark under-hair, and silky, black top-hair with irregular white markings. It is similar to the skunk, but is lighter, softer, less full, and has no disagreeable odor.

Cat, House.—18 × 9 inches. Is mostly black and dark brown, the best skins coming from Holland. The hair is weak, coming out with the friction of wear. In the trade, the black variety is known as genet.

Chinchilla.—12 × 7 inches. This is one of the rarest and most beautiful furs. It comes from Bolivia and Peru, where, due to the uncontrolled trapping of the animal, it is becoming scarce, and this compelled the governments to enact laws prohibiting the taking of chinchilla for a certain period. The fur is of a delicate blue-grey, with black shadings, the fur being 1–1¹⁄₄ inches deep. Unfortunately, the skin is quite perishable.

Chinchilla, La Plata.—9 × 4 inches. Incorrectly called “bastard chinchilla” in the trade. It is a similar species to the Bolivian chinchilla, but due to the lower altitude and warmer climate of its habitat, is smaller, with shorter and less pretty hair, the color of the under-hair being darker, and of the top-hair less pure. It is quite as undurable as true chinchilla.

Chinchillone.—13 × 8 inches. Is also from South America. The fur is longer, weaker, poorer and yellower than real chinchilla, but the skins are often dyed in shades closely resembling the natural chinchilla.

Ermine.—12 × 2¹⁄₂ inches. The under-hair is short and even, with the top-hair slightly longer. The leather is light, close in texture, and quite durable. In mid-winter the color is pure white, except the tip of the tail, which is usually quite black. The best skins are from Siberia.

Fisher.—30 × 12 inches, with tail 12–18 inches long. It is the largest of the marten family. The under-hair is deep, and of a dark shade, with a fine dark, glossy and strong top-hair, 2 or more inches long. The best skins are from Canada. The fur is something like a dark silky raccoon, while the tail, which is very highly prized, is almost black.

Fitch.—12 × 3 inches. It is of the marten species, and its common name is polecat. The under-hair is yellow and ¹⁄₃ of an inch deep. The top-hair is black, 1¹⁄₂–1³⁄₄ inches long, very fine and open in growth, and not so close as the martens. The largest and best skins are from Denmark, Holland and Germany. The Russian skins are smaller, silkier, and are usually dyed as a substitute for sable.

Fox, Blue.—24 × 8 inches. The under-hair is thick and long, while the top-hair is fine and not so plentiful as in other foxes. It is found in Alaska, Hudson Bay Territory, Greenland and Archangel. Although called blue, the color is really of a slaty or drab shade. The skins from Archangel are more silky and of a smoky bluish color, and being scarce are most valuable. The white foxes which are dyed a smoky blue are brilliant and quite unlike the browner shades of the blue-fox.

Fox, Cross.—20 × 7 inches. The skins generally have a pale yellow or orange tone, with some silver points, and a darkish cross marking on the shoulders, on account of which the animal got its name. Some are very similar to the pale red foxes of Northwest America. The darkest and best skins are from Labrador and Hudson Bay, those from lower latitudes being inferior.

Fox, Grey.—27 × 10 inches. Has a close dark drab under-hair, with coarse regular, yellowish, grizzly-grey top-hair. The majority of the skins come from Virginia and southwestern U. S. A. Those from the west are larger and brighter-toned.

Fox, Kit.—20 × 6 inches. The under-hair is short and soft, as is also the top-hair, which is a very pale grey mixed with some yellowish-white hairs. It is the smallest of the foxes, and is found in Canada and northern United States.

Fox, Red.—24 × 8 inches, although some kinds are larger. The under-hair is long and soft, and the top-hair is plentiful and strong. The colors range from pale yellow to a dark red, some being very brilliant. It is widely found in northern America, China, Japan, and Australia. The Kamchatka foxes are exceptionally fine and rich in quality. Farther north, near the open sea, the fur is coarse. The skins have an extensive use, both natural and dyed. They are dyed black in imitation of the black fox, or these when pointed with badger or other white hair to imitate the silver fox.

Fox, Silver.—30 × 10 inches. The under-hair is close and fine, and the top-hair, which is black to silvery, is 3 inches long. The fur on the neck usually runs almost black, and in some cases the black extends over half the length of the skin. When all black, it is a natural black fox, and is exceedingly rare and high-priced. The silver fox is very valuable, the finest wild skins coming from Labrador. The tail is always tipped white. The majority of the silver fox pelts that reach the market today are bred on ranches in Canada and the United States.

Fox, White.—20 × 7 inches. It is usually small and inhabits the extreme northern sections of Hudson Bay, Labrador, Greenland, and Siberia. The Canadian are silky-haired and inclined to a creamy color, while the Siberian are whiter and more woolly. The under-hair is generally of a bluish-grey tone, but the top-hair in winter is usually full enough to hide such a variation. Those skins which have under-hair that is quite white are rare and much more expensive than the others. In summer specimens of these species have slightly discolored coats, the shades resembling those of the blue fox. The skins which are not perfectly white are bleached, or if they cannot be bleached sufficiently white they are dyed various shades of smoke color, blue-greys and also imitation blue fox.

Goat.—The size varies greatly. The European, Arabian and East Indian varieties are used mainly for leather and wool. Many from Russia are dyed black for rugs. The hair is brittle, with poor under-hair, and is not durable. The Chinese export many skins in grey, black and white, made into rugs of two skins each. Frequently the skins are dyed black or brown in imitation of bear.

Hamster.—8 × 3¹⁄₂ inches. A destructive rodent found largely in Russia and Germany. The fur is very flat and poor, of a yellowish-brown color, with a little marking of black. On account of its lightness it is used for linings; occasionally it is dyed.

Hare.—24 × 9 inches. The common hare of Europe is used mostly for the hatters’ trade. The white hares of Russia, Siberia, and other northern regions are the ones mainly used for furs. It is whitest in mid-winter, and the fur on the flanks is longer than that on the back. The hair is brittle and not durable, and the leather is quite as bad. Yet the skins are used to dye imitations of more than a dozen different furs. The North American hares are also dyed black and brown.

Kangaroo.—The sizes vary greatly, the larger kinds being generally used for making leather. The sorts used for fur are, blue kangaroo, bush kangaroo, wallaroo, rock wallaby, swamp wallaby, and short-tailed wallaby. Many of the swamp wallabies are dyed imitation skunk, and look quite attractive. The colors are generally yellowish or brown, some in the swamp variety being dark brown. The skins are quite strong. The rock wallabies are soft and woolly, and often have a bluish tone. They are used for rugs.

Kolinsky.—12 × 2¹⁄₂ inches. It is of the marten family. The under-hair is short and rather weak, but regular, as is also the top-hair. The color is usually a uniform yellow. They are generally dyed in imitation of other members of the marten family. It is very light in weight, and the best skins are obtained from Siberia. The tails are used for artists’ “sable” brushes.

Lambs.—Those of commercial interest are from South Russia, Persia, and Afghanistan, and include Persian Lamb, Broadtail, Astrachan, Shiraz, Bokhara, Caracul, and Krimmers.

The Persians are 18 × 9 inches, and are the finest and best. When properly dressed and dyed they should have regular, close, bright curls, varying from small to very large and if of equal size, regularity, tightness and brightness, their value is inestimable.

All the above lambs, except krimmer, are naturally a rusty black or brown, and are in most cases dyed a jet black. Luster cannot be imparted where naturally lacking.

Broadtails, 10 × 5 inches, are the young of the Persians, killed before the wool has had time to develop beyond the flat wavy state. They are naturally of exceedingly light weight, and when of an even pattern possessing a lustrous sheen are costly. The pelt, however, is too delicate to resist hard wear.

Astrachan, Shiraz, and Bokhara lambs, 22 × 9 inches, are of a coarser and looser curl. Caracul lambs are the very young of the astrachan, and the finest skins are almost as effective as the broadtails, although not so fine in texture.

Krimmers, 24 × 10 inches are grey lambs obtained from Crimea. They are of a similar nature to the caraculs, but looser in curl, and ranging in color from a very light to a dark grey, the best being pale bluish-greys.

Slink lambs come from South America and China. The South American are very small, and generally those are still-born. They have a particularly thin pelt, with very close wool of minute curls. The Chinese sorts are much larger.

Leopard.—3 × 6 feet long. There are several kinds, the chief being the snow leopard or ounce, Chinese, Bengal, Persian, East Indian, and African. The first variety inhabits the Himalayas, and has a deep, soft fur, quite long as compared with the Bengal sort. The colors are pale orange and white with dark markings. The Chinese are of a medium orange-brown color and full in fur. The East Indian are less full and not so dark; the Bengal are dark and medium in color with short, hard hair. The African are small, with pale lemon-colored ground, and very closely marked with black spots.

Lynx.—45 × 20 inches. The under-hair is thinner than in the fox, but the top-hair is fine, silky and flowing, 4 inches long, of a pale grey, slightly mottled with fine streaks and dark spots. The fur on the flank is longer, and white, with very pronounced markings of dark spots, and this part of the skin is generally worked separately. Skins with a bluish tone are more valuable than those with a sandy or reddish hue. The lynx inhabits North America as far south as California. The best skins come from Hudson Bay, and also Sweden. They are generally dyed black or brown, similar to dyed fox.

Marmot.—18 × 12 inches. A rodent found largely in the south of Germany. The fur is yellowish-brown, rather harsh and brittle, and without under-hair. Also found in North America, China, and the best skins come from Russia. It is dyed brown in imitation of mink or sable, the stripes usually being put on in the completed garment.

Marten, Baum.—16 × 5 inches. Also called Pine Marten, and is found in the woods and mountains of Russia, Norway, Germany and Switzerland. It has a thick under-hair with strong top-hair, and ranges from a pale to a dark bluish-brown. The best are from Norway, are very durable and of good appearance, and a good substitute for the American sable.

Marten, Japanese.—16 × 5 inches. It is of a woolly nature with rather coarse top-hair, and quite yellow in color. It is dyed, but it is not an attractive fur, lacking a silky, bright and fresh appearance.

Marten, Stone.—Size and quality similar to the baum marten. The color of the under-hair is stony white, and the top-hair is a very dark brown, almost black. Skins of a pale bluish tone are used natural, while less clear colored ones are dyed, usually in Russian sable shades. They are found in Russia, Bosnia, Turkey, Greece, Germany, and France, the best coming from Bosnia and France.

Mink.—16 × 5 inches. Is of the amphibious class, and is found throughout North America, as well as in Russia, China and Japan. The under-hair is short, close and even, as is also the top-hair, which is very strong. The best skins are very dark, and come from Nova Scotia. In the central states the color is a good brown, but in the northwest and southwest, the fur is coarse and pale. It is very durable and an economic substitute for sable. The Russian species is dark, but poor and flat in quality, and the Chinese and Japanese sorts are so pale that they are always dyed.

Mole.—3¹⁄₂ × 2¹⁄₂ inches. Is plentiful in the British Isles and Europe, and is much in demand on account of its velvety fur of a pretty bluish shade. Although the skins are comparatively cheap, the cost of dressing is high on account of the considerable amount of labor involved. The pelt is very light in weight, but does not resist well the friction of wear.

Monkey, Black.—18 × 10 inches. The species usually found on the west coast of Africa, is the one of interest to the fur trade. The hair is very long, very black and bright, with no under-hair, and the white pelt is very noticeable by contrast.

Muskrat, Brown, Black, Russian.—12 × 8 inches. A very prolific rodent of the amphibious class, obtained in Canada and the United States. It has a fairly thick and even brownish under-hair, and a rather strong, dark top-hair of medium density. It is a durable and not too heavy fur. It is used natural, but recently the plucked, sheared and dyed skins have found a very extensive use as Hudson seal, an imitation of real seal. The so-called black variety of muskrat is found in New Jersey and Delaware, but only in comparatively small numbers. The Russian is also very small and limited in numbers. It is of a pretty silvery-blue shade with even under-hair, with very little silky top-hair, and silvery-white sides, presenting altogether a marked effect.

Nutria.—20 × 12 inches. Is a rodent about half the size of the beaver, and when plucked, has only about half the depth of fur, which is not so close. It is often dyed a seal color, but its woolly nature renders it less effective than the dyed muskrat. The skins are obtained from northern South America.

Opossum, American.—18 × 10 inches. Is a marsupial, the only one of its class found outside of Australia. The under-hair is of a very close frizzy nature, and nearly white, with long bluish-grey top-hair mixed with some black. It is found in central sections of the United States, and is frequently dyed imitation skunk.

Opossum, Australian.—16 × 8 inches. Is of a totally different nature from the American. Although it has fur-hair and top-hair, the latter is sparse and fine, so that the fur coat may be considered one of close even under-hair. The color varies according to the district of origin, from blue-grey to yellow with reddish tones.

Those from near Sidney are a light clear blue, while those from Victoria are a dark iron-grey, and stronger in the fur-hair. The most pleasing shade of grey comes from Adelaide. The reddest are the cheapest. The ring-tailed opossum, 7 × 4 inches, has a very short, close and dark grey under-fur, some almost black, but the skins are not used extensively. The Tasmanian opossum, grey and black, 20 × 10 inches, is of a similar description, but larger, darker, and stronger in the under-hair.

Otter, River.—The size varies considerably, as does also the length of the fur, according to the origin. It is found in greatest numbers in the coldest northern regions, and with the best under-hair, the top-hair being unimportant, as it is plucked out. Most of the best river otters come from Canada and the United States, and average 36 × 18 inches. The skins from Germany and China are smaller and shorter furred. The colors of the under-hair vary from very dark brown to almost yellow. Both the fur and the leather are extremely strong, and many skins are dyed imitation seal after plucking.

Otter, Sea.—50 × 25 inches. Is one of the most beautiful of furs. The under-hair is of a rich, dense, silky nature, with short and soft top-hair, which is not plucked. The colors range from a pale grey-brown to a rich black, and many skins have a sprinkling of white or silver-white hairs. The blacker the under-hair, and the more regular the silver points, the more valuable is the skin.

Pony, Russian.—This is a comparatively cheap, but very serviceable fur, and possesses some very desirable qualities. It has a thin leather, but is also scantily haired. Young pelts have a design on them somewhat similar to broadtail lambs, or moire astrachans, but this design is lost to a considerable degree by dyeing the furs. The hair, which is very glossy, is generally dyed black, although the natural pelts are also worn extensively.

Rabbit.—10 × 16 inches. The fur is thick and fine, but the pelt is very weak. It is a native of central Europe, Asia, North and South America, New Zealand and Australia. The color ranges from white to black. France, Belgium and Australia are the greatest producers of rabbits suitable for dyeing black, the so-called French seal, for which they are mostly used. At the present time the dyeing of rabbits constitutes a considerable percentage of the total fur-dyeing operations in this country. The most varied shades are produced on rabbit, and it probably is the basis of the greatest number of dyed imitations of better furs. In addition to the French seal, or sealine, rabbit is dyed in imitation of beaver, mole, etc.

Raccoon.—20 × 12 inches. Varies considerably in size, quality and color of the fur, according to the part of North America in which it is found. The under-hair is 1–1¹⁄₂ inches deep, pale brown, with long top-hair of a dark and silvery-grey mixture of a grizzly type, the best having a bluish tone, and the cheapest a yellowish or reddish-brown. The best skins come from the northern part of the United States. The skins have a wide use natural, but are also dyed dark blue, or imitation skunk, the latter being a very effective and attractive substitute, and extensively used. Sometimes the skins are plucked, and if the under-hair is good, the effect is similar to a beaver.

Sable, American and Canadian.—17 × 5 inches. The skins are sold in the trade as martens, but since many of the skins are of a very dark color, and almost as silky as Russian sable, they have come to be known as sable. The prevailing color is a medium brown, while many are quite yellow. These pale skins have been dyed so well that they can cheaply substitute Russian sable. The finest skins are from the Eskimo Bay and Hudson Bay districts, the poorest from Alaska.

Sable, Russian.—15 × 5 inches. Belongs to a species of marten similar to the European and American, but much more silky in the texture of the fur. The under-hair is close, fine and very soft, the top-hair is regular, fine and flowing, and silky, ranging from 1¹⁄₂ to 2¹⁄₂ inches in depth. In color they vary from a pale stony or yellowish shade to a rich, almost black, dark brown, with a bluish tone. The leather is exceedingly close and fine in texture, very light in weight, and very durable. The Yakutsk, Okhotsk, and Kamchatka sorts are good, the last being the largest and fullest-furred, but of less color density than the others. The most valuable, are the darkest from Yakutsk in Siberia, particularly those having silvery hairs evenly distributed over the skin, but these furs are very rare.

The Amur skins are paler, but often of a pretty, bluish tone, with many interspersed silvery hairs. The fur is not so close or deep, but is very effective nevertheless. The paler skins from all districts are now tipped, the tips of the hair being stained dark, the fastest dyes being used, and only an expert can detect them as differing from the natural shades.

Seal, Fur.—The sizes range from 24 × 15 inches to 15 × 25 inches, the width being the widest part of the skin after dressing. The most useful skins are the pups 42 inches long, the quality being very good and uniform. The largest skins, known as wigs, and ranging up to 8 feet in length, are uneven and weak in the fur. The supply of the best sort is chiefly from the northern Pacific, Pribilof Islands, Alaska, northwest coast of America, Aleutian Islands, and Japan. Other kinds are taken from the south Pacific regions. The dressing and dyeing of seal takes longer than for any other fur, but when finished, it has a fine, rich effect, and is very durable.

Seal, Hair.—This is chiefly used for its oil and leather, and not for its fur. It has coarse, rigid hair, and no under-hair.

Skunk, or “Black Marten.”—15 × 8 inches. The under-hair is full, and fairly close, with glossy, flowing top-hair about 2¹⁄₂ inches long. The majority of the skins have two stripes of white hair extending the whole length of the skin. These were formerly cut out, but more recently are dyed the same color as the rest of the skin. They are widely found in North and South America. The best are from Ohio and New York. The skunk is naturally the blackest fur, is silky and very durable.

Squirrel.—10 × 5 inches. This size refers to the Russian and Siberian types, which are practically the only kind imported for fur, other species having too poor a fur to be of great commercial interest. The back of the Russian squirrel has an even, close fur, varying from a clear bluish-grey to a reddish-brown, the bellies in the former being of a flat quality and white, in the latter, yellowish. The backs are worked up separately from the bellies. The pelts, though light in weight, are tough and durable. The tails are dark and very small, and considerably used.

Tiger.—The size varies, the largest measuring about 10 feet from the nose to the root of the tail. It is found throughout India, Turkestan, China, Mongolia, and the East Indies. Coats of the Bengal variety are short and of a dark orange-brown with black stripes. Those from other parts of India are similar-colored, but longer in hair, while those from the north and China are not only large in size, but have very long soft hair of a delicate orange-brown, with very white flanks, and marked generally, with the blackest of stripes.

Wolf.—50 × 25 inches. Is closely allied to the dog family, and very widely distributed over the world. The best are the full-furred skins of a very pale bluish-grey with fine, flowing black top-hair, from the Hudson Bay district. Those from the United States and Asia are harsher and browner. The Siberian is smaller than the North American, and the Russian still smaller. A large number of prairie-dogs, or dog-wolves, is also used for cheaper furs.

Wolverine.—16 × 18 inches. Is a native of America, Siberia, Russia, and Scandinavia, and is of the general nature of the bear. The under-hair is full and thick, with strong, bright top-hair about 2¹⁄₂ inches long. The color is of two or three different shades of brown on one skin, the center being dark, and presenting the general appearance of an oval saddle, bordered with a rather pale shade of brown, and merging to a darker shade towards the flanks. This peculiar character stamps it as a distinguished fur. It is expensive, and quite valuable on account of its excellent qualities.

Wombat, Koala or Australian Bear.—20 × 12 inches. It has a light grey or brown, close, thick under-hair ¹⁄₂ inch deep, and no top-hair, with a rather thick, spongy pelt. It is cheap, and well suited for rough wear.

CHAPTER II
STRUCTURE OF FUR

Fur is made up of two main components, the hair and the skin, and each of these has a very complex structure.

In the living animal the skin serves as a protective covering, and also constitutes an organ of secretion and of feeling; consequently it is of a highly complicated nature. The skin of all fur-bearing animals is essentially the same in structure, although varying considerably as to thickness and texture. It consists of two principal layers, which are entirely different in structure and purpose, and correspondingly different in both physical and chemical respects: the epidermis, epithelium or cuticle, which is the outer layer, and the dermis or corium, which is the true skin. ([Fig. 1A]).

The epidermis is very thin as compared with the corium. Its outer layer consists of a tissue of cells, somewhat analogous to the horny matter of nails and hair. The inner surface, called the ‘rete malpighi,’ rests on the true skin, and is a soft, mucous layer of cells. These cells are spherical when first formed, but as they approach the surface become flattened, and dry up, forming the horny outer layer of the epidermis, which is constantly throwing off the dead scales, and which is constantly being renewed from below. It is from this inner layer of the epidermis that the hair, the sweat-glands, and the fat-glands are developed.

The corium, or true skin, consists essentially of white, interlacing fibres of the kind known as connective tissue. These fibres are themselves made up of extremely fine smaller fibres, or fibrils, cemented together by a substance of a somewhat different nature from the fibres, the coriin. Towards the center of the skin, the texture of the interweaving fibres is looser, becoming much more compact at the surface just beneath the inner layer of the epidermis. This part of the corium is so exceedingly close that the fibrils are scarcely recognizable. It is in this part that the fat-glands are situated, while the hair-roots and sweat-glands pass through it into the looser texture of the corium. The surface next to the flesh is also closer in structure than the middle portions of the skin, and has somewhat of a membranous character due to the fibres running almost parallel to the surface of the skin. The skin is joined to the body proper by a network of connective tissue, frequently full of fat-cells. This layer, together with portions of the flesh which may adhere to it, is removed by the process called ‘fleshing,’ and this side of the skin is known as the flesh side. The corium also contains a small proportion of yellow fibres, known as ‘elastic fibres,’ which differ physically and chemically from the rest of the skin substance.

During the course of the development of the embryo animal, a small group of cells forms like a bulb on the inner side of the epidermis, above a knot of very fine blood-vessels in the corium. This group of cells grows downward into the true skin, and the hair-root which is formed within it, surrounds the capillary blood-vessels, drawing nourishment from them, and thus forming the papilla. ([Fig. 1A]). Smaller projections also form on the bulb, and the fat-glands are gradually developed. The sweat-glands are formed in a manner similar to the development of hair.

The individual hair fibre is quite as complicated in structure as the skin, and is made up of four distinct parts. ([Fig. 1B]).[2]

The medulla, or pith, is the innermost portion of the hair, and is composed of many shrunken cells, often connected by a network which may fill the medullary column partially or wholly.

Surrounding the medulla is the cortex, which is made up of spindle-shaped cells fused into a horny, almost homogeneous, transparent mass, and forming a large proportion of the hair shaft.

In the majority of the fur-bearing animals, there is distributed within and among the cells of the cortex a pigment in the form of granules or minute particles, arranged in the different hairs in fairly definite and characteristic patterns. It is to these pigment granules that the color of the hair is due primarily. In some cases the coloring matter of the shaft is uniformly diffused and not granular.

Fig. 1

The outermost coat of the hair, or cuticle, is composed of thin, colorless, transparent scales of varying forms and sizes, and arranged in series like the shingles of a roof. It is on these scales that the lustre or gloss of the hair depends. Since lustre is due to the unbroken reflection of light from the surface of the hair, the smoother the surface, the glossier it will appear. When the scales of the cuticle are irregular and uneven, the surface of the hair will not be uniform and smooth, and the light reflected from it will be broken and scattered, and consequently the hair will not possess a high degree of lustre. As a rule, the stiff, straight hairs have the most regular and uniform arrangement of the scales of the cuticle, and hence are the smoothest and glossiest.

Fur hairs are in general either circular or elliptical in cross-section, those which are circular being straight or only slightly curved, while those which are elliptical in cross-section are curly like the hair of the various kinds of lambs.

Most fur-bearing animals have two different kinds of hair on their bodies. Nearest to the skin is a coat of short, thick, soft and fine hair, usually of a woolly nature, and called the under-hair, under-wool, or fur-hair. Overlying the fur-hair is a protective layer of hair, longer and coarser than the under-hair, and usually straight, hard, smooth and glossy. This is called the top-hair, over-hair, guard-hair or protective hair. In some furs, the top-hair constitutes one of the chief elements of their beauty, while in others, the top-hairs are removed, so as better to display the attractive features of the under-hair. The roots of the top-hair are generally deeper in the skin than those of the fur-hair, and in some instances where the top-hair is removed, as in the seal, the roots are destroyed by the action of chemicals applied to the skin side, the roots of the fur-hair being wholly unaffected by this treatment.

The fur-hair and the top-hair in the same animal have different medullary and cuticular structures, and these characteristics may be used to distinguish the two kinds of hair. [Figs. 2A and B] illustrate these differences. In each case, the two large hairs on the left of the illustration are the guard-hairs, showing respectively the cuticular scales and the medulla. On the right are the two fur-hairs showing the scales and the medulla.

Although composed of many different kinds of tissues, and varying so greatly in physical structure, both the skin and the hair belong to the same class of chemical compounds, namely the proteins. These are highly complex substances, forming the basis of all animal and vegetable tissues. There are many different kinds of proteins, varying somewhat in their constitutions, but all show, on analysis the following approximate composition of chemical elements:

The principal kinds of proteins found in the various fur structures are albumins, keratin, collagen, and mucines. Albumins, of which the white of egg is the most familiar variety, occurs to some extent in the corium as serum in the blood-vessels, and also as the liquid filling the connective tissues, known as the lymph. They are soluble in cold water, but when heated to about 70° C., they coagulate and are then insoluble. Concentrated mineral acids and strong alcohol will also effect coagulation.

Fig. 2
A. Hair of European Beaver.	B. Hair of Skunk.
a. Top-hair. b. Under-hair.	a. Top-hair. b. Under-hair.

Keratin is the chief substance of which all horny parts of the animal body are composed, such as the hair, nails or hoofs. It is the principal constituent of the hair, the epidermis, and the walls of the cells of the inner layer of the epidermis, or the ‘rete malpighi.’ Keratin is particularly rich in sulphur, and is quite insoluble in cold water. Caustic alkalies attack keratin-containing parts.

The collagens are the principal proteins of the skin, forming largely the substance of the connective tissue fibres, and consequently the framework of the skin. They are insoluble in cold water, dilute acids and salt solutions, and are only very slowly attacked by dilute alkalies. Dilute acids and alkalies cause collagen to swell; concentrated acids, vegetable tanning materials, basic chrome or iron salts cause it to shrink. By boiling with water, dilute acids or dilute alkalies, collagen is split up into gelatin or glutin.

The mucines of the skin, intercellular material or coriin, are soluble in dilute acids, in dilute solutions of alkalies and of alkaline earths such as lime, and in 10% salt solution, but insoluble in water, and in salt solutions of greater or less concentration than 10%. On drying the skin, the mucines cement the connective tissue fibres, causing the skin to become stiff, horny and translucent. The mucines are also constituents of the cells of the ‘rete malpighi.’ The solubility of the mucines in dilute solutions of alkalies and of alkaline earths causes the epidermis to be loosened from the corium, when the skins are treated with such solutions for some time.

When raw skins are boiled with water, the greater part goes into solution, the residue consisting chiefly of the keratins of the hair and epidermis cells. On cooling, the solution solidifies to a jelly of gelatine. It combines with both acids and alkalies. A property of the skin which is of importance in the tanning operation of fur-dressing, and a quality which also characterizes gelatine, is the capacity to absorb liquids and swell up, without changing chemically. Raw pelts swell up easily in pure cold water, but much more easily in solutions of dilute acids or dilute alkalies, only a little of the skin material being dissolved. In stronger solutions, the skins swell up less, while more of the skin substance dissolves, and by prolonged action of strong acids or alkalies, an almost complete solution of the skin is obtained, without, however, any of the material decomposing. With very strong alkalies or acids, the skin substance is broken up into simpler compounds, such as various amines and ammonia. The swelling action of acids or of alkalies increases with the increase in concentration of the acid or alkali, but only up to a certain point, after which further increase in the strength of the acid or alkaline solution causes a reduction in the swelling, and even produces shrinkage. In the presence of neutral salts, like common table salt, sodium chloride, the swelling action of acids, is reduced, but the action of alkalies remains practically unaffected.

When treated with the various chemicals, fur hair acts in a manner quite similar to wool. If it be remembered that certain classes of furs are derived from animals of the sheep family, such furs as Persian lamb, krimmer, etc., it becomes apparent why chemicals should affect furs in nearly the same way as wool. The great majority of furs differ from those of the sheep family, in possessing much greater resistance to the action of chemicals. The range is a wide one however, and no exact criterion can be adopted. As a general rule, the reactions are most marked with fur-hair of a woolly nature, so this may be taken as a standard of reference.

Acids have relatively little action on the hair, when applied in dilute solutions. The scales of the cuticle or epithelium are somewhat opened, the fibre becoming slightly roughened thereby. Even at high temperatures, the hair is quite resistant to the action of dilute acids. Concentrated acids destroy the hair with the liberation or formation of ammonia, hydrogen sulphide, and various amino acids. When treated with dilute acids, the hair, especially if it is of a very woolly nature, retains considerable quantities of acid, this phenomenon being probably due to the fixation of the acid by the basic groups in the hair. Nitric acid produces a yellow coloration when applied in dilute solution for a short time. Sulphurous acid, the acid formed by the burning of sulphur, has a bleaching action on the hair.

Alkalies attack the hair, even in dilute solutions, and by longer action complete decomposition sets in, with formation of ammonia and amino-acids. Ammonium carbonate, soap, and borax are practically harmless in their effect on the hair. Sodium and potassium carbonates roughen the hair on prolonged action, even in dilute solutions. Calcium hydroxide on continued action removes sulphur from the hair, causing it to become brittle.

Salts of alkalies and alkaline earths do not affect the hair at all. Salts of the heavy metals on the other hand, are absorbed in appreciable quantities. From a dilute solution of alum, aluminum hydroxide is absorbed by the hair, the potassium sulphate remaining in solution. Similarly with copper, iron, and chromium salts, the metal oxides are fixed by the fibre.

CHAPTER III
FUR DRESSING
Introductory and Historical

Fur dressing has a twofold purpose. First of all, the putrefactive processes must be permanently stopped, so that the skin may be preserved as such, or worked up as some fur garment, without danger of decomposition. Having taken measures to assure the endurance or relative permanency of the pelt, the prime consideration is, of course, the appearance of the hair. The hair must be so treated that all its inherent beauty is brought out to the fullest extent. It must be made clean and soft, and all the natural gloss must be preserved, and if possible, enhanced. The appearance of the leather is relatively unimportant, since it is not seen after the furs are made into garments. There are, however, certain qualities which it is essential for the leather to possess after being dressed, and these are, softness, lightness of weight, elasticity or stretch, and a certain firmness or ‘feel.’ In other words the important considerations in fur dressing are the employment of means, and the exercise of care to preserve or even improve those characteristics of the pelt which make it valuable.

The dressing of furs has many features in common with the manufacture of leather, which is a kindred art. But whereas in fur dressing the prime consideration is the appearance of the hair, and the leather is of secondary importance, in the production of leather, the hair plays no part at all, since it is entirely removed from the pelt. The fundamental points of resemblance between leather manufacture and fur dressing are in those processes and operations which are concerned with the preservation of the leather, and rendering it in the proper condition for use.

Both leather dressing and fur dressing have an origin which may be regarded as identical, and which dates back to the haziest periods of antiquity. In the course of satisfying his needs, primitive man killed the animals about him, and thus obtained his food. The killed animal also furnished a skin, which after undergoing certain manipulations and other treatments, could serve as a protective covering, ornament, or defensive weapon. Since the skin in its natural state was hardly fit for use because of its easy tendency to putrefaction, it is evident that man had to find some means of preventing this decay in a more or less permanent fashion, and moreover had to treat the skin so that it would be suitable for use, by rendering it soft and flexible. The discovery of means to accomplish these purposes was probably one of the first great steps forward on the path of progress and civilization.

There are evidences of the use of animal skins in the earliest periods of antiquity, in fact it is a usage which may be literally regarded as “old as the hills.” One of the earliest written records of the employment of the skins of animals as garments, is in the Old Testament, where it states, “Unto Adam and to his wife did the Lord God make coats of skins, and clothed them.” Numerous other biblical references indicate the use of animal skins for various purposes, sometimes prepared as leather, with the hair removed. Among the Egyptians tanning seems to have been a common occupation. The particularly attractive skins, like those of the leopard or panther, were especially prized, and were made up as furs for ornamental wear, rugs and decorations. The less valuable skins were unhaired and made into leather. Although the tanning or leather-producing processes of the Egyptians are quite unknown, numerous figures engraved in stone afford an indication to some of the manipulatory operations, such as soaking the skins, fleshing, softening with stones, stretching over a three-legged wooden “horse,” etc. Many articles, made of leather, have been found in the various Egyptian sarcophagi, and all are in a splendid state of preservation, after forty centuries, thereby indicating a very efficient method of dressing animal skins. Likewise, the presence in the museums of various articles, leather and fur, of Assyrian, Phoenician and Persian origin, tends to show that these peoples also possessed a considerable degree of proficiency in tanning. Frequent references in the Greek literature show that leopard and lion skins were worn as war cloaks, and they undoubtedly were properly made. In the Iliad is described an operation for the preparation of skins for use as garments, and the method seems to be a sort of chamois dressing.

The first method of tanning skins was, in all probability, that of rubbing into the skins various fatty materials found close at hand, such as parts of the animal, fat, brains, milk, excrement, etc., such an operation constituting the basis of what is now known as the chamois dressing. One of the reasons for believing that it was the first process to be used by primitive man, is the fact that certain undeveloped tribes and races of the present day still dress skins by it. The American Indians, even to this day prepare skins by rubbing in, on the flesh side, the brains of the animals which furnished the skins. The Eskimos dress skins by rubbing in animal fats or fish-oil, and subsequently softening and stretching the skins with their teeth in place of, or for want of other implements. Usually, however, variously shaped stones or bones of animals are used to obtain the proper degree of softness and flexibility. It is true, too, that some of the skins dressed in this primitive fashion can scarcely be excelled by any dressed with more modern processes and tanning methods.

The next step forward in the preparation of animal skins for use was undoubtedly the utilization of substances found in the earth. Common salt, sodium chloride, was the most universally used substance of mineral origin, just as it is today. Our prehistoric ancestors eventually discovered the preservative action of salt, and applied it to skins. While it was effective, it was not sufficiently permanent, so another mineral, also of very common and wide occurrence was used in combination with the salt, and the result proved quite satisfactory. This second common mineral was alum. The use of alum, which is the basis of numerous tanning processes to this day, seems to have been quite a popular method of ancient times. Artemidorus, a Greco-Roman writer, mentions the use of alum by the Greeks, and the Romans are known to have prepared a soft, flexible leather called aluta (alum leather), by using it. In view of the fact that Egypt had extensive deposits of alum, it is believed that the alum-salt process was employed also by the Egyptians in the preparation of leather. However, the evidence on this point is not conclusive.

One of the most important methods of producing leather, either as such or on furs, was with the aid of certain vegetable extracts, known as the tannins, from which the process of tanning gets its name. The discovery of the value of these materials for converting the decaying raw skin into a leather which could be preserved for an almost indefinite length of time, and which was flexible and soft as desired, was of far-reaching importance. For it is only in very recent times that these tannins have been superseded in part by new tanning substances whose use is simpler and more time-saving. Yet there are unmistakable indications that the tannins were employed for tanning at a period which reaches back to the dawn of history. Although it is scarcely probable that the people who used these materials could have known of the existence or the nature of the particular substances in the vegetable extracts which actually effect the tanning action, experience taught them to employ these plants which possessed the highest content of active ingredients, and which, consequently, were most effective in use. Tychios, of Boetius, a Greek supposed to have lived about 900 B.C. and mentioned in the Iliad, is considered the oldest known tanner, and was regarded by Pliny, a Roman writer, as the discoverer of tanning, and of the use of the various vegetable tanning materials. At any rate, the Greeks used the leaves of a so-called tanning-tree, which was probably the sumach. The Egyptians worked with the acacia, while the Romans used as tanning materials the barks of the pine, alder and pomegranate trees, also nut-galls, sumach and acorns. The Romans were quick to employ methods used by the peoples whom they conquered, and it is in this way that they learned the use of many of the plants mentioned, for tanning purposes.

Many other ancient peoples had various processes of tanning, the methods probably differing in each country. Thus the Chinese, Syrians, and much later, the Moors, were each known for proficiency in a certain class of leather tanning. It has been said that in general, even up to modern times, tanning with nut-galls was the characteristic method of the Orient; with oak-tan, that of the Occident, while the use of alum is regarded as the method peculiar to the Saracens.

In prehistoric times and the early centuries of civilization, skins or pelts were prepared for use by the individual, the work usually being done by the housewife and daughters, while the masculine members of the family were engaged in hunting the animals and obtaining the skins. At a later period, when people had advanced to the point where they lived in cities, the preparing or dressing of skins became centered in the hands of a comparatively small number of people, and thus the work took on the aspects of a trade. The workers in fur were at first the same people who made leather out of the skin, for the two kinds of work were very closely associated. During the period of the Roman supremacy, historical records show that the furriers, who did all the work connected with furs, from purchasing the raw skins, dressing them, making them into garments, to selling the latter, were organized into associations together with the leather workers. After the fall of the Roman empire, and throughout the centuries known as the Dark Ages, all traces of the furriers seem to have been lost, but in the beginning of the Renaissance period in the fourteenth and fifteenth centuries, we again find records of the furriers, who were now all members of the furriers’ guilds, also in association with the leather workers. As formerly, all the work connected with the production of fur apparel from the raw furs, was done by the master furrier and his apprentices. The methods and the implements used, were essentially the same as in Roman times, and in fact, up to a very recent period there was very little change in either.

With the advent of the great industrial era at the beginning of the nineteenth century, the guild system became ineffective, but the furriers continued their work as heretofore. Up to about the middle of the nineteenth century, the furrier continued to be the only factor of any importance in the fur trade. There was no need for speed in his work, for the demands of the trade were not so urgent. The fact that the dressing of furs often occupied two to four weeks was no deterring factor in his business. However, with the great expansion of the fur trade about this time, it became impossible for the individual furrier to do everything himself, and keep up with the requirements of his customers. Specialization commenced, and establishments were set up solely for fur dressing. The traditional time- and labor-consuming processes were still used, but the efficiency of work on a large scale enabled the fur dressers successfully to fill their orders. But the fur trade continued to grow by leaps and bounds, and very soon the fur dressers were no longer able to meet the demands of the trade. It was then that the science of chemistry came to the aid of the fur dresser, and helped him meet the exigency. By devising dressing processes which were cheap and efficient, and which only required several hours, or at the most one or two days, as compared with as many weeks, the chemist brought the fur dresser out of his dilemma. And with the adoption of mechanical time- and labor-saving devices, the fur dressing industry has made wonderful progress.

CHAPTER IV
FUR DRESSING
Preliminary Operations

The fur dresser receives the skins in one of two shapes, flat or cased, depending on the manner in which they were removed from the animal. Flat skins, as for example, beaver, are obtained by cutting on the under side of the animal from the root of the tail to the chin, and along the inner side of the legs from the foot to the first cut. The skins are either fastened to boards or attached to wooden hoops slightly larger than the skins, so as to stretch them, and are then carefully dried, avoiding direct sunshine or artificial heat, as it is very easy to overheat the skins and thereby ruin them. The great majority of skins, however, are cased. The pelts are cut on the under side of the tail, and along the hind legs across the body, the skin being then removed by pulling it over the head off the body like a glove, trimming carefully about the ears and nose. The skin is thus obtained inside out, and is drawn over a stretching board or wire stretcher of suitable shape and dimensions, so as to allow the skin to dry without wrinkling. The pelts, after drying in a dry, airy place, are removed from the stretchers and are ready for the market. With some furs, as foxes, the skins are turned hair-side out while still somewhat moist, and then put on the stretcher again till fully dried. In most cases, however, skins are sold flesh-side out. Throughout the various dressing operations cased skins are kept intact, being turned flesh-side out or hair-side out according as the processes are directed to the respective sides. The pelts are only cut open if they have to be dyed, or after the manufacturer receives them, when they have to be worked into manufactured garments.

A distinction which is made by fur dressers and dyers, and also by the fur trade in general, divides furs into those derived from domestic animals, particularly the various kinds of sheep, including also the goat species, and those obtained from other animals by trapping. In fact, at one time, and to a certain extent even to-day, dressers were divided into two groups based on this distinction, one class dealing only with furs obtained from the sheep family, and the other working with other kinds of furs. This differentiation is not a simple arbitrary one, but has a rational justification. As mentioned before, the manner and habit of living of the animal are important factors in determining the nature and constitution of its skin, both leather and hair. The structure of the body being dependent primarily upon the nature of the food absorbed by the animal, it is only natural that herbivorous or vegetable-eating animals such as sheep and goats, should possess fur of a different sort from that of the carnivorous or meat-eating animals, such as the majority of fur-bearers are. It also seems clear that furs differing in their character and constitution should require somewhat different treatments, and accordingly the methods are modified when furs like lambs or goats are dressed. To a great extent, however, the fundamental operations are similar for all furs, regardless of nature or origin, and these will be discussed briefly.

Inasmuch as the first great purpose of fur dressing is to render the skins more or less permanently immune from the processes of decay, it is necessary to prepare the pelts so as to be most fit to receive the preserving treatment. The skins as they are delivered to the fur dresser have, in the majority of cases, been stretched and dried to preserve them temporarily, while in some instances, especially with the larger furs like bears and seals, they are salted and kept moist. The flesh-side of the pelt still has considerable fleshy and fatty tissues adhering to it, and the hair is generally soiled and occasionally blood-stained. In order to get the pelts into such a condition that they can be worked and manipulated, they first have to be made soft and flexible. Very greasy skins are scraped raw in order to remove as much as possible of the attached fat, the operation being known as beaming or scraping. The typical beam, shown in [Fig. 3], consists of a sloping table usually made of some hard wood, and placed at an angle of about 45°. It is generally flat, although in some instances convex beams are also used, about a yard long, 8 to 10 inches wide, and firmly supported at the upper end. The skin is placed on the beam, flesh-side up, and is scraped with a two-handled knife ([Fig. 4]), always in a downward direction.

Fig. 3. Beam.

Fig. 4. Knives Used in Fur Dressing.

The first step in softening the skins is to get them thoroughly moistened, and this is variously done, depending on the nature of the skin. Lambs, for example, require the gentlest means of wetting them, while rabbits can stand soaking in water for several days. The manner and duration of moistening must be adjusted to the character of the pelt. For the putrefactive processes which were stopped by stretching and drying the skins, continue as soon as the pelt is again moistened. The progress of decay causes the evolution of certain gases, the simplest of which is ammonia, and eventually, if permitted to proceed, brings about the complete disintegration of the skin tissue. It has been found that a certain amount of gas formation is necessary to loosen up the fibres in order to get the best quality of leather after tanning. This process must be interrupted at the proper time and not allowed to proceed too far.

Skins which have been preserved fresh by salting, require only a comparatively short time (about 2 hours) to become softened by soaking in clean, soft water. Most dried skins need a longer treatment before they are sufficiently flexible. The addition of certain substances to the water facilitates and accelerates the softening. In some instances salt water is used for soaking the pelts, the preservative action of the salt tending to prevent any loosening of the hair. A solution of ¹⁄₄% borax is very effective in rendering the skins soft, and clean as well. Borax has an exceedingly mild alkaline action, and causes a slight swelling of the skin tissue, which then absorbs the water more readily. Being also preservative and antiseptic, borax tends to prevent decomposition of the skin tissue. Another chemical of a different nature, but equally effective is formic acid, used in the proportion of 1.5–2.5 parts per 1000 parts of water. Formic acid also induces a swelling of the skin, the pelts being soaked in a short time, and the antiseptic action of the acid obviates the possibility of the hair becoming loose. The water used should be fresh and clean, and the soaking must be stopped as soon as the skins have become soft and flexible. Sometimes the skins are allowed to soak overnight in water, while in other cases, the pelts are just moistened by dipping in water until thoroughly wet, and then laying them in a pile for several hours, or overnight. Another method which is practised with certain types of skins is the use of wet sawdust or of sawdust moistened with salt water. The fur skins are either embedded in the sawdust or drummed with it for several hours, or until sufficient moisture has been absorbed to render them flexible. By this means there is no danger of the skins being over-soaked, or of the hair being loosened. When the skins have been properly wetted, they are drawn with the flesh-side across the edge of a dull knife-blade, in order to help loosen the texture of the skin. They are then put into a tramping machine and worked until completely softened. In the case of large or heavy skins, the moistened pelts are worked on the beam with a dull beaming knife to impart thorough softness and flexibility.

The pelts are then cleaned with particular reference to the hair. With some furs this is accomplished simply by drumming for several hours with dry sawdust, whereby the oil and dirt are removed from the hair, and the hair is then freed from the sawdust by caging. Other skins are washed, being passed through a weak soap solution for a short time, the dirty spots being brushed. Occasionally an extract of soap-bark is used in place of the soap, being even more effective. The cleansed skins are then thoroughly rinsed to remove any of the cleaning material, which would affect the gloss of the hair if allowed to remain on the skins. Then in order to eliminate as much as possible of the water in the skins, they are hydro-extracted, a centrifugal machine of the type shown in [Fig. 5] being used. The basis of its action depends on the utilization of the principle of centrifugal force. The machine consists essentially of a perforated metal basket generally made of copper, capable of being rotated at a high speed. Surrounding the basket is an iron framework, polished or enamelled on the inside. The wet skins are placed in the rotating basket, fur side toward the perforations, and the water which is thrown off from the skins passes through the little holes, and is caught up on the walls of the outside frame, from where it is led off through suitable ducts. The centrifugal device is properly equipped with balancing and regulating attachments, as well as with a brake. The power may be applied by the over-drive or the under-drive as is most desirable in the particular case. The inner surface of the basket can also be enamelled or otherwise made resistant to the action of acids or other chemicals.

Fig. 5. Centrifugal Machine.

(Fletcher Works, Inc., Philadelphia)

When the skin is removed from the animal, as much as possible of the adhering fat and flesh is scraped off, but in spite of this, and in spite of subsequent beaming by the fur dresser, there is always a thin layer of flesh and fatty material remaining and this must be removed so as to expose the corium, enabling the efficient action of the chemicals used in the tanning processes. The process of removing this undesirable layer from the flesh-side is known as fleshing. It is a rather delicate operation, requiring considerable experience and dexterity on the part of the worker, for it is exceedingly easy to cut into the skin and damage the fur. A fleshing knife of the type commonly used is shown in [Fig. 6]. It consists of a sharp blade fastened at a slight angle from the vertical, with the cutting edge away from the workman, who straddles the bench, and by drawing the skins back and forth across the edge of the blade, removes all flesh and fat, leaving the corium free and clean. Large skins cannot conveniently be fleshed in this fashion. They are placed on the beam, and fleshed with a fleshing or skiving knife similar to the beaming knife, but consisting of a slightly curved, sharp two-edged blade having handles at both ends. Frequent attempts have been made to use suitable machines to do this work. A type of machine which has met with considerable success is depicted in [Fig. 7]. It is fashioned after the models used for the fleshing of hides for leather manufacture, and has special adjustments and regulating devices which afford protection for the hair part of the fur. From time to time other fleshing machines are put on the market, yet none of them seems to enjoy any great popularity, for fleshing is still largely a manual operation. With some classes of pelts, fleshing presents some difficulties, and chemical means have to be resorted to in order to loosen the flesh sufficiently to enable proper fleshing. In the case of large furs like bears, leopards, and the like, which while of no great importance in the fur trade, are occasionally met by the fur dresser, the skins after being soaked, and washed with soap-water, are partially dried; then the flesh-side is treated with technical butter or oil, which is tramped in. A mixture of salt water and bran is then applied to the skins, thereby causing a swelling action to set in, and the flesh becomes loosened, and is easily removed by fleshing on the beam. Seals receive a special treatment which makes them soft, and gives them greater stretch after they are tanned. A paste made by mixing a very dilute solution of caustic soda with an inert substance like French chalk, china clay, etc., is applied to the corium after the skins have been fleshed, then the pelts are folded up, and allowed to lie for several hours. They are then entered into a dilute solution of calcium chloride and left overnight. After being washed in a paddle or drum, first with fresh water, and then in water containing lactic or formic acid to remove the lime, the skins are ready for tanning.

Fig. 6. Fleshing Knife on Bench.

Fig. 7. Fleshing Machine.

(Turner Tanning Machinery Co., Peabody, Mass.)

CHAPTER V
FUR DRESSING
Tanning Methods

After the pelts have gone through the preliminary operations of softening, washing and fleshing, they are ready to receive the treatment which will convert the easily decomposing skin into leather of more or less permanency, depending on the method used.

During the past century, considerable study has been made both by scientific and technical people, of the problem of leather formation. Numerous theories as to the nature of the process have been evolved, but even to this day, no satisfactory explanation has been given which would account for all the facts as they are now known, so the matter is still a subject of considerable controversy. Procter, who is one of the leading authorities on leather today discusses the development of the tanning theories as follows:

“The cause of the horny nature of dried skin is that the gelatinous and swollen fibres of which it is composed not merely stiffen on drying but adhere to a homogeneous mass, as is evidenced by its translucence. If in some way we can prevent the adhesion of the fibres while drying we shall have made a step in the desired direction, and this will be the more effective the more perfectly we have split the fibre-bundles into their constituent fine fibrils, and removed the substance which cements them. The separation of the fibres can be partially attained by purely mechanical means.... Knapp, to whom we owe our first intelligible theories of the tanning process, showed that by physical means the separation and drying of the fibres could be so far effected as to produce without any tanning agent a substance with all the outward characteristics of leather, although on soaking it returned completely to the raw hide state. He soaked the prepared pelt in absolute alcohol, which penetrated between, and separated the fibres and at the same time dried them by its strong affinity for water. More recently, Meunier has obtained a similar result by the use of a concentrated solution of potassium carbonate which is even more strongly dehydrating.

“Knapp made a further step by adding to his alcohol a small quantity of stearic acid which, as the alcohol evaporated, left a thin fatty covering on the fibres which completely prevented their adhesion, and reduced their tendency to absorb water; and he so produced a very soft and white leather. Somewhat similar are the principles of the many primitive methods which apply fatty and albuminous matters, grease, butter, milk, or brains to the wet skin, and by mechanical kneading and stretching, aided by capillarity, work these matters in between the fibres as the water evaporates. Such methods are still used, and enter into many processes in which other tanning agents are also employed.

“Building upon these facts, Prof. Knapp advanced the theory that the effect of all tanning processes was not to cause a change in the fibres themselves, chemical or otherwise, but merely to isolate and coat them with water-resisting materials which prevented their subsequent swelling and adhesion. True as this theory undoubtedly is in many cases, it can hardly be accepted as the whole truth, and it seems incontestable that frequently the fibres themselves undergo actual chemical changes which render them insoluble and nonadhesive.

“Before Knapp’s work, the prevalent theory, at least as regards vegetable tannage, had been a chemical one, started by Sir Humphrey Davy. If a solution of gelatine be mixed in proper proportion with one of tannin, both unite to form a voluminous curdy precipitate; and, according to Davy’s ideas, this was amorphous leather. Against this, it was urged that even the supposed ‘tannate of gelatine’ itself could not be a true chemical compound, since the proportions of its constituents were considerably varied by changes in the strength of the solutions, or by washing the precipitate with hot water; and further, that in chemical compounds, the form was changed, and no trace of the original constituents appeared in the compound; while in leather apart from some change of color and properties, the original fibrous structure remained unaltered.

“This reasoning appears much less conclusive now than it did in Knapp’s day. Against the last objection guncotton may be quoted as an instance of profound chemical change with no alteration in outside appearance; and it is recognized that, especially among complex organic substances, chemical reactions are rarely complete, but that stable positions are reached, so-called ‘equilibria,’ in which the proportion of changed and unchanged substance is dependent on concentration or other conditions; and that therefore such a precipitate might well be a mixture of gelatine with a true gelatine tannate from which further portions of tannin might be dissociated by water.

“With the clearing up of old difficulties, however, the conflict between chemical and physical theories has, as is usually the case, merely passed into a new phase. Years ago, it was shown by Linder and Picton and others, that liquids could be obtained which were not really solutions of ions or molecules, but merely suspensions like that of clay in water, or butter-fat in milk; but so finely divided as to appear clear and transparent, and pass through filters like true solutions. Later, by means of the ultra-microscope their discrete particles have actually been made visible, each of them consisting of many molecules of the suspended substance. Nevertheless, these particles have many molecular properties, possessing plus or minus electrical charges; behaving like large ions under the influence of an electrical current; and mutually precipitating and neutralizing each other when positive and negative are brought together. Such solutions are called ‘colloid,’ and those of gelatine and tannin are of the class, so that it is now often said that the precipitation of gelatine by tannin, and the fixation of tannin by gelatinous fibre are merely ‘colloidal’ and ‘physical,’ and not ‘chemical’ phenomena. Admitting the facts, the question still arises whether the distinction between chemical and physical is not here one without a difference; and whether between the purely ionized dilute solution of a salt and the coarsely granular clay suspension there is any point where a definite line of demarcation can be drawn. The writer inclines to the view that there is not; and that ionic and colloidal combinations are extreme cases of the same laws, both physical, and both chemical.”

There are several methods which are used in tanning furs, each having its peculiar characteristics and qualities, and possessing individual advantages and disadvantages. In order to be able to judge the merits of the various processes, it is necessary to have a criterion which can serve as a basis of reference. Fahrion, a recognized authority and investigator in this field, gives a definition of leather which is usually accepted as a standard for comparison. He says: “Leather is animal skin, which on soaking in water and subsequent drying does not become hard and tinny, but remains soft and flexible; which does not decay in the presence of cold water; and which does not yield any gelatine on boiling with water.” While the requirements set forth in this statement are essential for leather, and a compliance with them would also be desirable for tanned furs, a somewhat less rigorous standard of conditions to fulfil is satisfactory for the general needs and purposes of furs. The chief qualities which tanned furs must possess, with particular reference to the leather side of the pelt, are retention of softness and flexibility after being moistened by the furrier for manufacturing purposes, and subsequent drying; and freedom from a tendency to decay during this operation and thereafter. If the furs are to be dyed, the effect of the dyeing must also be considered, and the tanning must be such as to enable the dyed furs to possess the above qualities.

The most important tanning processes employed for furs are the following:

• 1. Salt-acid tan, or pickle.
• 2. Mineral tans.
• 3. Chamois tan.
• 4. Formaldehyde and similar tans.
• 5. Combination tans.
• 6. Vegetable tan.

1. Salt-acid Tan, or Pickle

This is one of the most extensively used methods for tanning furs, and is also very cheap and easily applied. A typical formula for this tan is the following: A solution of salt is prepared containing about 10% of common salt, sodium chloride, and to this is added ¹⁄₂–³⁄₄ ounce of sulphuric acid for each gallon of tanning liquor. The proportions may be varied within certain limits, but the figures here given are those which have proven successful in practise. The solution should be made in a wooden or earthenware container, free from any metal, as it would be attacked by the acid. The liquor is then applied to the flesh-side of the fleshed skins by means of a brush, making sure to touch all parts of the pelt. They are then placed in a pile and allowed to remain thus until tanned, an operation which occupies a time ranging from a few hours to two or three days depending on the thickness of the skins. When the corium has lost its translucence and has become of a milky-white color throughout the entire thickness of the skin, as can be seen by viewing a cross-section, the skin may be considered tanned. In some instances, where the hair of the fur can stand immersion without injury, the skins are entered into the pickling solution and allowed to remain for 12 to 24 hours, which is generally a sufficient time to tan them in this manner.

The acid of the pickle causes the skin to swell, the salt then penetrating between the fibres of the corium, and at the same time reducing the swelling of the skin. The acid also neutralizes the alkaline products of decomposition which may form, while the salt acts as a deterrent to the progress of the putrefactive processes. When the skin is dried after tanning, and stretched and finished, a soft white leather is obtained which is permanent as long as it is kept dry. It is the salt which causes the fibres of the skin to be completely differentiated and thus prevents their adhesion.

It is interesting to note that other acids besides sulphuric can be used for the pickle, organic as well as mineral, formic acid in ¹⁄₄% solution being especially effective and giving excellent results, but is more expensive than the mineral acid. A method, which in principle is identical with the pickle, but carried out in an entirely different manner, is the lactic acid fermentation process, or “Schrot-beize” as it is called in German. The procedure is in general as follows: “The fleshed skins are placed on tables, flesh-side up, and covered with a layer of bruised barley grains, or a mixture of 3 parts of wheat bran and 2 parts of rye flour. Then the head, tail and legs are turned inward, and the skins rolled up in little cushions, hair-side out, and placed in a vat. When this is filled with the skins a solution of common salt is poured over them, and they are allowed to remain thus in a moderately cool place for 24 hours. After this time, the skins are carefully unrolled, so as not to remove any of the adhering solid materials, and turning the skins hair-side inward, they are laid flat together in pairs and placed in an empty vat. After another 24 hours they are again unpacked and replaced in another vat, care being taken each time to keep all the solid particles adhering to the flesh-side. This operation is continued and repeated until the skins are properly tanned, which takes from 10 to 14 days, depending on the weather and the temperature. The skins are then removed, rinsed free of the tanning substances, pressed, dried and finished.” A somewhat modified form of this process is the so-called Russian tan, which is usually done in the following manner: 5 parts of bruised barley grains are mixed with ten parts of luke-warm water in a vat, which is then covered up. A small quantity of brewers’ yeast is also added to aid in the fermentation. As soon as the mixture develops a slight heat, one part of fresh whey is added, and the fleshed skins entered into the tanning liquor in which they remain for about 12 hours. They are then tramped in the mixture so as to effect greater penetration, and left until the tanning process is complete. Whey is the milk fluid left after the casein and most of the fat have been removed from the milk by coagulation, and consists practically of a solution of all the milk-sugar or lactose, and the lactic acid of the milk, together with a small percentage of mineral salts, and a slight amount of fat. By fermentation, the milk-sugar is converted into lactic acid, which helps to effect the tan by swelling the skin.

The effectiveness of the fermentation processes depends to a considerable degree on the action of certain bacteria and yeasts. Bacteria are one-celled organisms belonging to the vegetable kingdom, and some are so small as to be scarcely visible under a microscope, while some indeed cannot be seen by any means, their existence being inferred from their effects. As they vary in size, bacteria also vary in shape, some being spherical, others in the form of long, thin rods, while still others are of a spiral shape; another common form is the dumb-bell shaped bacterium. Some types are provided with what are known as flagella, which resemble fine hairs attached to the body of the organism, and which enable it to move about actively in liquids. The food of bacteria is always in liquid form, as only in this condition can it be absorbed. However, some kinds of bacteria attack solid substances from which they obtain their nourishment, but this is done in an indirect way, by secreting certain fluids known as enzymes, which dissolve or digest the material and convert it into a form that can easily be absorbed by the bacteria. The enzymes are non-living chemical substances, which possess the peculiar property of bringing about the chemical change of an almost indefinite amount of material upon which they act, without themselves being in any way changed. Yeasts also act in a manner similar to the bacteria in causing various chemical changes, particularly inducing fementations. In the simple “Schrot-beize,” the starch contained in the bran or barley grains is first converted to a soluble sugar by means of enzymes secreted by the bacteria which are always present. This sugar then undergoes an acid fermentation, with the formation of lactic and acetic acids, due in this case to organisms known as the bacterium furfuris A and B. The action of the Russian tan is similar, but quicker. In this case, the sugar is already present in soluble form, and the yeast cells cause its fermentation with the production of lactic acid. In both cases, the acids as they form swell and loosen up the skin fibres slowly, the salt penetrating between them, and keeping them separated on drying. Both methods give results which are equally good, but by the Russian tan the skins acquire a disagreeable odor, which makes this method of dressing objectionable.

The lactic acid fermentation processes have an advantage over the pickle, in that the slow formation of weak organic acids with their gradual action produce a softer leather, with a gentler ‘feel,’ the presence of the flour and the grains of the tan, aside from their tanning action, contributing to the fullness and softness of the leather. There is also less likelihood of the leather being subsequently affected by the presence of the acid in it, as lactic and acetic acids are much less injurious than sulphuric acid to leather. These disadvantages of the pickle can to a large degree, be overcome without any great difficulty. On the other hand, the matter of the length of time of the tanning process, shows the acid pickle at a great advantage, and so, especially for furs other than those obtained from sheep and goats, the pickle is in most cases used as the principle method of tanning. In Austria, Russia, and to a certain extent in Germany also, the “Schrot-beize” is still considerably employed, chiefly for dressing sheep and lamb skins. The dressing of the various kinds of Persian lambs, caraculs, astrachans, etc., in the native center of the industry in Buchara and surrounding districts, is also a “Schrot-beize,” barley, rice flour or rye flour, and salt water being used to prepare the skins, the manipulations being essentially the same as those described above, although carried out in cruder and more primitive fashion.

2. Mineral Tans

The basis of the tanning of furs by means of solutions of mineral compounds is the fact that the basic salts of certain metals are capable of producing leather. It has been found that compounds of aluminum such as alum or aluminum sulphate, or any other soluble neutral salt of aluminum, possess tanning powers. Other metals which are capable of forming salts of the same type are also endowed with the quality of converting skin to leather under suitable conditions, chromium and iron being the most important metals in this connection. Chemically these metals all belong to the same group, and have properties which are very similar in many respects, the characteristic of most importance for tanning purposes being the quality of forming soluble basic salts by the addition of alkalies or alkaline carbonates to solutions of their neutral salts, or in certain instances simply by the action of water upon these neutral salts. By neutral salts are meant those in which the metallic content is combined with the normal proportion of acid; while basic salts are those in which the acidic portion is present in less than the normal ratio, being partially replaced by a hydroxide group. When the acid part of the salt has been entirely replaced in this way, the compound is called a hydroxide or hydrate of the metal. Between the neutral salt and the hydroxide several different basic salts are possible, some being soluble, while others are insoluble. If into a solution containing a basic salt of either aluminum, iron or chromium a skin be entered, a part of the basic salt will be precipitated on it in insoluble form. Inasmuch as neutral salts of these metals when dissolved in water split up to a small degree, into free acid and soluble basic salt, a skin immersed in such a solution will also absorb the basic salt in an insoluble form. Upon these facts in general, depends the action of the mineral tans used in tanning furs.

A. Alum Tan

The alum tan is one of the oldest methods of producing leather, being employed by the Romans about two thousand years ago, and it is believed, by the Egyptians at a much earlier period. Its extensive use in Europe, however, dates from the time of the conquest of Spain by the Moors, who introduced the process.

At the present time, rabbits and moles are tanned by this process, as are also at times other furs such as muskrats, squirrels, sables, martens, etc., when a better tan is desired than that produced by the pickle. Ordinary alum, which is a double sulphate of aluminum and potassium, and aluminum sulphate are the chief compounds used for this tan. In recent years, the aluminum sulphate has to a considerable degree replaced the alum for tanning, inasmuch as it can be cheaply obtained in a sufficiently pure form, and contains about one and one-half times as much active aluminum compound as does alum.

While the aluminum salt can be used alone for tanning, it produces a stiff, imperfect leather, so salt is always added. The ratio of the salt to the aluminum sulphate or alum can vary within rather wide limits, the mixtures used in practise ranging from one part of salt to four parts of the aluminum compound, up to equal parts of both, or even in some formulas, a greater proportion of salt than of the other constituent. Ratios which are most common are four of alum to three of salt, or two of alum to one of salt.

When aluminum sulphate is dissolved in water, a small part of it splits up into a soluble basic salt and an equivalent amount of free acid. The reaction may be shown as follows:

When a skin is entered into such a solution, the free acid is absorbed, causing a swelling of the pelt. While this is taking place, a further quantity of the neutral aluminum salt splits up into more basic salt and free acid. At the same time the basic aluminum sulphate is also taken up by the skin, probably attaching itself to some of the acidic groups contained in the skin substance, in a manner analogous to the combination of the acid with the basic groups of the skin substance. A point is reached, however, when the skin is no longer able to take up more of the basic salt, for the presence of the acid undoubtedly acts as a deterrent. The skin, if dried after such a treatment contains a small amount of aluminum, which is insufficient to tan the pelt properly, and as a result this comes out in an undesirable and quite useless condition. If to the solution of the aluminum sulphate salt is added, a different result is obtained. To a certain extent the salt acts here as in the pickle. The skin on absorbing the free acid of the solution naturally swells, but the salt reduces this swelling, and at the same time, by penetrating between the fibres and dehydrating them, produces a leather as in the pickle. In addition, the presence of the salt enables a greater amount of basic aluminum sulphate to be formed, and thus a greater quantity is taken up by the skin. On drying and stretching after such a treatment, a soft, flexible and stretchable leather is obtained.

The number of formulas for tanning furs by this process is legion, the principle being the same in every instance, and mixtures of salt and alum or aluminum sulphate form the basis of the various tans. Following are a few typical formulas, which have been found to be of practical value:

A solution is prepared by dissolving 7.5 lbs. of alum and 3 lbs. of common salt in 20 gallons of water. When cool, the clean, fleshed skins are entered, being paddled or drummed for a short time and then allowed to remain until tanned. By this method the hair also takes up some of the alum, and if the skins are to be dyed, unevenness may result. In order to avoid this, the tanning may be effected by brushing a stronger solution on the pelt. A mixture of 4 lbs. of alum and 3 lbs. of salt, dissolved in 8 gallons of water, and made into a paste by the addition of 4 lbs. of flour, is applied to the flesh-side of the skins. These are then placed in pairs, flesh-side together, and allowed to remain in a pile until tanned. Sometimes a second application is given. The flour may be omitted, but it serves to cause the tanning mixture to adhere better to the skins.

Still another method is the following: Into the flesh of the moist, fleshed skins is rubbed a mixture of two parts of dry powdered alum with one part of salt. After allowing time for it to be absorbed, another application is given, rubbing in well, and especially treating the thick parts. The pelts are then folded up, or rolled together, flesh-side in, and placed in a vat or tub, which is covered up to prevent drying. They are left so until tanned, as shown by examination and test. They are then rinsed, hydro-extracted and dried, and after stretching and finishing, a soft, white, pliable leather is obtained.

B. Chrome Tan

By using chrome alum instead of ordinary alum, together with salt, skins can be tanned, but the leather formed is not altogether satisfactory. The basic principle here is the same as in the alum tan, depending on the formation of soluble basic chrome sulphates in the solution of a neutral sulphate. The method employed at the present time, the so-called one-bath process as distinct from the two-bath process, which cannot be applied for tanning furs, involves the production of the basic chrome sulphate by the addition of an alkali or an alkaline carbonate to the solution of the neutral salt. It was Prof. Knapp who first published this process as early as 1858; but it was not until 1893 that it was shown to be of practical value, and was then patented in this country by Martin Dennis. Since that time it has been in general use with but slight modifications.

The chrome tan is used only to a limited extent in the tanning of furs, the method requiring very careful treatment and accurate supervision during the various stages of the process, and the leather coming out colored a pale-blue-green tint, which for some purposes is objectionable. In some plants ponies and rabbits are tanned with chrome; and when the skins are to be dyed by means of certain coal tar dyes, they have to receive a chrome tannage. The leather produced by a chrome tan is very durable, and possesses great resistance to the action of water.

Any salt of chromium, with either mineral or organic acids, can be used, but chrome alum is the one most commonly employed. If a skin is entered directly into a solution of a chrome salt made basic with an alkali, the precipitation of the insoluble basic salt will take place very rapidly, and the tanning will be only superficial. The procedure is therefore first to treat the skins with a chrome solution which forms only small quantities of the basic salt. After the skins are impregnated with the solution, this is made basic, so that the real tan will take place within the skin tissues among the fibres of the corium. A common formula is the following: 5 lbs. of chrome alum are dissolved in 10 gallons of water. The skins are entered into the solution at about 70° F. and paddled for about 2 hours, or drummed for one hour. Then a solution of three pounds of washing soda is added slowly to the liquor which is then stirred up well, and the skins drummed or paddled again for an hour or two, and then left in the liquor for 12 to 24 hours till completely tanned. The skins are rinsed, and washed in ¹⁄₂% solution containing ²⁄₃% of the weight of the skins of borax. The pelts are then well washed in clean water, hydro-extracted and dried.

C. Iron Tan

Tanning by means of iron salts has thus far been merely a matter of scientific interest and has not found any practical use. The principle involved is identical with that of the preceding mineral processes.

3. Chamois Tan

The chamois dressing, as previously noted, is undoubtedly the oldest method of preparing leather from skin, the various fat-containing substances derived from animals, fish, birds, etc., being used for the purpose. The chief object of the fat was to coat the fibres of the skin, thus preventing their adhesion, and at the same time rendering them resistant to water. In the true chamois tan, the fat seems to have also a chemical function in contradistinction to the other which is merely physical or mechanical. For, if skins tanned by the chamois process be treated with a weak solution of an alkali, all the fatty materials should be removed thereby, but this happens only to a small extent, the pelt retaining its softness and pliability, and the other characteristic qualities of leather, indicating that the fat is combined intimately with the skin substance in a permanent fashion.

In tanning furs, various oils and fats are used, but not all are capable of producing a chamois tan. Among the fatty materials are mineral oils, and vegetable and animal oils and fats. Mineral oils are the distillation products of petroleum, partially liquid, and partially solid. Being inert substances, they have no tanning effect, but serve merely as water-proofing or fattening materials. Except for their oily nature they have nothing in common with fats, being quite unaffected by solutions of alkalies or of acids.

Vegetable and animal fats and oils are, when pure, neutral substances formed by the combination of fatty acids with glycerine. They possess the property of saponification, that is, of forming a soap when treated with an alkali, the soap being the alkaline salt of the fatty acid. Under certain conditions, the fat can be split up into free fatty acid and glycerine by the action of acids, or even water alone. Some fats on long standing, split up in this way spontaneously in the presence of moist air. As a general rule, those fats which exhibit this property to a marked degree are affected by contact with the air, due to the absorption of oxygen which reacts chemically with the fats, forming what are known as oxy-fatty acids, usually less soluble, and having a higher melting point than the original fats. Vegetable and animal fatty materials are classified on the basis of this phenomenon of absorbing oxygen from the air, those possessing this quality to a great degree being called “drying oils,” others being “partially drying,” or “non-drying.” Olive oil, castor oil, cocoanut oil and cottonseed oil are examples of non-drying or partially-drying vegetable oils, linseed oil being the most important drying-oil in this class. Tallow, lard, butter-fat, neats-foot oil are non-drying animal fats, the drying oils being seal oil, whale oil, and cod-liver oil.

Fig. 8. Tramping Machine or “Kicker.”

(F. Blattner, Brooklyn, New York.)

For tanning purposes, this property of absorbing oxygen is important, because only with drying oils can a true chamois tan be obtained, non-drying oils acting like mineral oils only as water-proofing materials. The details of the chamois process are not quite clear, there being considerable difference of opinion on the matter. But all the studies on the subject tend to prove that there are at least two phases to the process: first, the mechanical covering of the fibres with the fat, this property being common to all fats or oils which may be used; and second, the combination of the fat with the skin in some chemical way, as a result of the oxidation of the fat, a characteristic found only in the drying oils. During the oxidation of the fats, the glycerine in them is converted to acrolein or acryl-aldehyde, which also aids the tanning. It was at one time supposed that the tanning action was due to this aldehyde alone, but a chamois tan can be made with fatty substances from which all the glycerine has been removed. The evidence on this question, however, is not quite conclusive.

In general, the procedure of the chamois tan is as follows: The hydro-extracted, fleshed skins are rubbed on the flesh-side with a good quality of seal-oil. They are then folded up, and put into a ‘kicker,’ where they are tramped for two or three hours to work in the oil. The kicker is a machine such as shown in [Fig. 8] consisting of a receptacle for the skins, and two wooden hammers which work up and down mechanically, turning and pounding the skins. (As many as 1000–1500 skins of the size of musk-rats can be worked at one time in such a machine.) The pelts are then taken out and hung up in a warm room for several hours, considerable oxidation taking place. Another coat of oil is then applied, which is again tramped in, and the skins are hung up once more and exposed to the air to cause the oil to oxidize. After the skins are sufficiently tanned they are rinsed in a weak soda solution to remove the excess oil, washed and dried. When skins with fine hair such as marten, sable, mink, etc., receive a chamois tan, they are not tramped in kickers as the delicate top-hair will be broken, and the value of the skin thereby reduced. Instead they are placed in small drums, together with metal balls of varying sizes and weights depending on the particular fur treated, and the oil is worked in by rotating the drum. Such a ball-drum, as it is called, is shown in [Fig. 9].

Fig. 9. Ball Drum.

(F. Blattner, Brooklyn, New York.)

In conjunction with the chamois tan may be discussed the process of oiling, inasmuch as the method of application and the effect are both similar to the chamois tan up to a certain point. It is customary to treat skins tanned by any other method but the chamois process, with some oil in order to render them more impervious to water. The greatest variety of oils and fats can be used, the action in most cases being simply the mechanical isolation of the skin fibres by such a substance, thus corresponding to the first or physical phase of the chamois tan. The chemical phase, if it takes place at all, is usually slight, and is merely incidental. Oiling is generally applied either before drying after tanning, or after drying, the oiled skins being placed in a kicker and tramped to cause the oil to penetrate. In some instances the oiling material is put in the same mixture as the tanning chemicals, and the tanning and oiling are effected simultaneously.

Among fatty substances used for oiling are mineral oils, such as paraffine oil, and vaseline; animal fats, like train oils, butter, egg-yolk, glycerine, neats-foot oil; vegetable oils, like olive oil, castor oil, cottonseed oil; also sulphonated castor oil and sulphonated neats-foot oil. These may be used singly or in various mixtures, an emulsion of an oil and a soft soap also being frequently employed.

4. Formaldehyde Tans

Formaldehyde has proven to be of great value in the tanning of furs, usually in conjunction with other processes. Formaldehyde is a gas with a strong, irritating odor, and its 40% solution, which is the customary commercial form, also possesses this quality. When skins are treated for several hours with a very dilute solution of the commercial product, a leather is obtained which combines the properties of the alum tan and the chamois tan. Moreover, in the majority of observed cases, where furs have been tanned with formaldehyde, the skins seem to acquire a certain immunity to the attacks of vermin and moths. Although the skins do not in any way retain the odor of the formaldehyde, nevertheless these destructive agents seem to be repelled.

Numerous processes have been devised which use formaldehyde in connection with other substances for tanning. Thus in a German patent is described a method involving the alternate or simultaneous treatment of pelts with solutions of formaldehyde and alpha or beta naphthol. Both the formaldehyde and the naphthol exercise tanning actions, but the process is not used in practise.

In 1911, Stiasny, a well-known leather chemist produced a synthetic substance by the condensation of formaldehyde with a sulphonated phenol, forming an artificial tannin. This chemical, called “Neradol D,” exhibits many of the properties characteristic of true tannins, although in no way related by structure and composition. By the use of “Neradol D” a soft, white and flexible leather is obtained, and it is therefore a suitable tanning material for furs.

5. Combination Tans

In many instances more than one method is employed in tanning the furs, and in this way what is known as a combination tan is produced. While the various individual processes described give more or less satisfactory results by themselves, they generally possess some features, which for certain purposes may be undesirable, and which can be eliminated or considerably reduced by using other processes at the same time or subsequently. Some of the combination methods are, pickle with chrome tan, alum tan with chrome tan, and formaldehyde tan with pickle, mineral tan or chamois tan. By means of such combinations various qualities of tanned furs can be obtained, and if it is desired to produce a pelt having certain special characteristics, this can be brought about by combining two or more standard methods.

Some illustrations of combined tannages are the following: Alum-chrome tan. The skins are tanned by the regular alum process, then the constituents of the chrome tan are dissolved directly in the same bath, and the chrome tan is effected as usual. Chrome-formaldehyde tan. To the regular chrome tan solution is added ¹⁄₂ lb. of formaldehyde for every 10 gallons of chrome liquor. The rest of the process is as ordinarily.

6. Vegetable Tans

In practise, the vegetable tanning matters are not used for furs, although in some special instances gambier cutch may be employed occasionally with some other tan. However, many of these tannins also have dyeing properties, and are used in dyeing the furs. In this connection it must be mentioned that furs dyed with these materials also receive a vegetable tan, which improves the quality of the leather to a considerable extent.

Comparison of The Various Tanning Methods

In choosing a method for tanning any particular kind of fur, several factors must be considered. The nature of the pelt, insofar as it is weak or strong; the time, labor and cost of materials required by the tanning process; the effect on the leather of the different dyes and chemicals used in dyeing, if the skin is to be dyed, are a few of the points requiring attention and consideration.

For furs which are only to be dressed, a simple tan like the pickle will suffice in most cases. Special instances, such as the rabbit and mole already mentioned, and a few other furs are tanned by the alum method. The pickle is undoubtedly the cheapest and simplest method of tanning skins, and yields a soft, white leather which is permanent as long as it is kept dry. If it is put into water, about 25% of the salt contained within the pelt dissolves out, and the acid present swells up the tissues. If the skin is dried in this condition, it will come out hard and brittle, tending to crack very easily. By treating the leather before drying with a strong salt solution, a good deal of the extracted salt will be replaced, and on drying and stretching, it will work out soft. Skins tanned by the “Schrot-beize” are affected by water in quite the same manner as the pickled skins.

The alum tan gives a leather similar to that produced by the pickle, but with the advantage that the skins possess greater stretch and flexibility. In its resistance to water, the alum-tanned pelt is quite as susceptible as the other. As a general rule, the skin absorbs about 6% of its weight of alum from the tanning solution, but gives up three-quarters of this when it is soaked in water, producing on drying, a hard, stiff leather. The chrome tan is especially impervious to water, easily resisting temperatures of 80° C., and even boiling water. It is employed to only a limited extent on account of the special effort and care required to obtain satisfactory results, also because the pelt acquires a pale blue-green color which is not desired on dressed skins. The chamois tan, and some of the combinations of the formaldehyde tan with the other methods, give very soft, flexible leathers which possess a sufficiently great resistance to the effects of water and heat.

In tests made to determine the best working temperatures for dyeing skins dressed by the salt-acid tan, and for skins dressed by the chamois process, some very interesting facts were brought out. These two tans were chosen because they represent opposite extremes, the salt-acid tan usually giving the poorest results, and the chamois tan giving the best results in practise in dyeing. Other methods, except the chrome, range between these two. The procedure in these experiments was to treat the skins at ordinary temperatures in water, or dilute solutions of the various chemicals and dyes usually employed in dyeing, and then heat these solutions until the leather just began to shrink and shrivel up. This point, called the shrinking point (S.P.), gave the temperature to which the skins could be subjected in the given solution without danger to the pelt. (The experiments and observations were made by Erich Schlottauer, while director of a large German fur dressing and dyeing plant).

The first observation made was that different furs tanned by the same process were affected differently in the same solutions. Thus in plain water, three furs, all tanned by the acid-salt tan, had shrinking points varying by several degrees; similarly with two different furs tanned by the chamois process, there was a variation in the shrinking point of two degrees. The explanation of this discrepancy among the different skins may be that there was a slight difference in the conditions under which they were tanned, experiments showing that a maximum difference of 4° C. may exist among skins tanned by the same process, but not under the same or identical circumstances. Another reason for the variation may be the fact, that some skins are more greasy than others, and are thus more resistant to the effects of water or of some chemicals. The furs with the higher shrinking points in water were those which naturally are more greasy than the others.

Weak solutions of acids tend slightly to lower the shrinking point, while weak solutions of alkalies appreciably raise it, in both chamois-tanned and salt-acid-tanned skins. Solutions of dyes and mordants as a general rule increase the resistance of the skin to heat, varying quantities of these substances having no, or little different effects on the shrinking points. Previous treatment of the leather with some oil considerably raises the shrinking point of the pelt. Formaldehyde effects a great increase of the resistance of the skins to heat, especially with chamois-tanned furs. The experiments in this case were made by first treating the skins in the weak formaldehyde solution, and then determining the shrinking point in plain water.

Two skins, both dressed by the “Schrot-beize,” a Persian lamb and an astrachan, after dyeing had shrinking points almost 10 degrees higher than when undyed. The extra tannage which the skins received from the tannins used in the dye mixtures for these furs, accounts for this increased resistance to heat.

The following tables give the observed figures in the different experiments:

Table I

A—Water

B—Water plus 1% Ammonia (s.g. 0.910)

C—Water plus 1% Sulphuric acid (66° Beaumé)

Table II

A—1000 c.c. water plus 40 c.c. Peroxide plus 5 c.c. ammonia

B—500 c.c. water plus 2 grams Ursol D (Para-phenylene-diamine)

C—500 c.c. water plus 5 grams Ursol D

Table III

A—500 c.c. water plus 5 grams ground nut-galls

B—300 c.c. water plus 2 grams pyrogallic acid

C—500 c.c. water plus 2 grams potassium bichromate

D—Water, after treating leather with rapeseed oil

Table IV

A—500 c.c. water plus 5 c.c. formaldehyde for 1 hour

B—500 c.c. water plus 5 c.c. formaldehyde for 12 hours

C—500 c.c. water plus 10 c.c. formaldehyde for 3 hours

D—As in C, but treated with 500 c.c. water plus 5 c.c. ammonia, instead of water alone.

Table V

A—Before dyeing

B—After dyeing

As a result of these experiments it may be concluded that the maximum temperature for drying salt-acid tanned skins should be 40° C., while for chamois tanned skins the temperature may be permitted to reach 45° C. without any danger of the leather being affected. Moreover, in the case of pickled skins, the matter of extraction of the tanning agent, as well as that of the leather becoming “burned” may be effectively counteracted by brushing some oil or fat on to the leather side before dyeing the pelt.

The shrinking points of skins dressed by the various tanning methods are constant within certain limits, depending on the nature of the skin and on the conditions of tanning, and it is possible by observing the shrinking point, in conjunction with other characteristics of a given pelt, to determine what method of tanning was used.

CHAPTER VI
FUR DRESSING
Drying and Finishing

One of the most important operations of all the fur dressing processes is the drying of the skins. For even when all the previous steps have been successfully completed, there is still a great possibility of the skin being injured if the drying is not properly and carefully carried out.

The essential requirements for good drying are proper temperature, uniformity and rapidity. The leather part of the fur cannot, in the moist state, resist temperatures exceeding about 45° centigrade, for when dried, the skin turns out hard and stiff, and cracks easily. The furs must therefore be dried at an initial temperature of 25° to 30° centigrade, and as the moisture is gradually removed, the temperature may be raised, for the less water that remains in the pelt, the less is the leather affected by the heat, and the more difficult is the removal of its aqueous content.

If the drying process is not a uniform one, that is, if all the skins in a lot are not subjected to the same drying conditions, then after the drying has proceeded for a certain time, some skins may be quite dry while others are not, or there may be as many different degrees of dryness as there are skins drying. There is also the possibility of great variation in the amount of moisture removed from different parts of the same skin. Such a state of affairs requires an extra expenditure of time, labor and heat power in order to get the whole lot of furs into a more or less uniform condition. Moreover in some kinds of furs, especially those with thick skins, when the drying is not even, there is danger of the epidermal layer drying away from the corium, and subsequently peeling and cracking. Uniformity of drying requires the maintenance of a reasonably constant temperature equally distributed throughout all parts of the space where the drying is done, so that all the furs may be dried under the same conditions.

Rapidity of drying is desirable not only because it is beneficial to the condition of the pelt, but also from the point of view of practical business economy. The space occupied by the drying should be as small as possible compatible with the volume of work, and with the efficiency of operation. Slow drying involves the use of much space to take care of all the skins to be dried, or an accumulation of pelts ready to be dried, neither of which conditions is efficient or desirable.

It was formerly the general custom, still practised in some establishments, to dry the skins by hanging them up, leather-side out on lines in a large room or loft, the heat being usually supplied by steam pipes. Such a procedure occupied often as long as two or three days to get complete drying, involved a great deal of labor, and the results were far from uniform. In fact, in order to get the skins more nearly equable, it was necessary to subject them to an additional operation. This usually consisted of rotating the skins in a closed drum for several hours, the constant intermingling of the pelts in contact with each other causing any moisture left in them to be evenly distributed throughout the whole lot. The skins, by this process also are rendered somewhat softer and more flexible, but by drying under proper conditions the entire extra operation can be dispensed with, the furs coming out quite as soft and flexible without the drumming.

A great improvement was the adoption of large fans to circulate the heated air in the loft, thereby approaching more nearly an even temperature. More modern devices have, however, been developed, whereby drying can be effected in the most uniform manner, with perfect control of temperature, and requiring the least possible consumption of space, time, labor and power. A typical arrangement consists of a large closed chamber, generally constructed of steel, and divided into several compartments each of which may be operated independently of the others. Air, heated over suitably located steam pipes to the required temperature, is forced through the various compartments by means of fans operated by power. The conditions may be varied in each compartment, as to temperature or humidity, both of which can easily be regulated, or all the compartments may be used together as one unit. The skins are hung up on rods or lines in the compartments, or on special frames for the purpose, which are then entered into the compartments and the doors shut. The dry, heated air is forced to pass over the skins, and takes up their moisture. At the further end of the drying chamber is another fan which removes the moisture-laden air after it has done its work. The drying is effected in from 6 to 24 hours, and all skins are obtained in the same condition, for the process is quite uniform and regular.

Within recent years there has been evolved a highly efficient and economical drying equipment, based on a somewhat different principle than underlies any of the foregoing methods. The conveyor type of dryer, as it is called, is admirably suited to the needs of the fur dressing and dyeing industry, and is undoubtedly superior to any of the previous systems of drying furs, in that it affords an enormous saving of space, time, labor and power, and gives greater uniformity and presents better working conditions.

Fig. 10. Diagrammatic Views of Conveyor Dryer.

a. Side View; b. End View.

(Proctor & Schwartz, Inc., Philadelphia.)

The conveyor dryer consists essentially of a steel enclosure, through which the skins pass on horizontal conveyors. Where special insulation is necessary, asbestos panels are used to line the enclosure, making the dryer absolutely fireproof, and enabling the maximum utilization of heat. In the middle of the dryer are located the steam coils which furnish the heat, and in many instances exhaust steam can be used as the source of heat. [Figure 10] shows diagrammatically the arrangement and operation of the conveyor type of dryer. The enclosure is divided into several compartments, in each of which a different condition of temperature and humidity is maintained, the temperature being closely and accurately regulated by an automatic control, and once the dryer has been set for any condition, all skins will be dried exactly the same, regardless of weather or season.

Fig. 11. Conveyor Dryer.

(Proctor & Schwartz, Inc., Philadelphia.)

The skins to be dried are placed on poles which in turn are set on the horizontal conveyors as in [Fig. 11]. As the skins pass through the compartments, large volumes of air, heated to the required temperature over the steam coils, are circulated among the skins by means of the fans. Exhaust fans, properly placed, remove a certain quantity of moisture-laden air when it has accomplished its full measure of work. When the skins on the conveyors have passed the full length of the dryer, they are entirely dry, and are then removed from the poles. ([Fig. 12]). The time required for drying varies according to the nature of the fur from 1–2 hours to 6–8 hours. In tests made to determine the relative efficiency of the conveyor type of dryer as against the old “loft” method, it was found that there was a saving of over 50% in power, and of 85% in floor space, as well as a great saving of labor, when the conveyor system was used, the number of skins dried in a given period of time being the same in both cases. The advantages of the new method are easily apparent, and the saving is sufficiently great with large lots of furs, to make an appreciable difference in the final cost of dressing.

If the skins have been dried by a modern drying system they all come out in a uniform condition, and are ready to go on immediately to the next operation. If, however, a form of the “loft” method of drying has been used, it is customary to subject the skins to an additional process. The dried pelts are put in drums with damp sawdust, and drummed for a short time in order to get them into the proper condition. The drumming is essential for the purpose of equalizing the condition of the pelts, some being drier than others, and as a consequence of the contact with the moist sawdust, they are all brought to the same degree of dryness. As a result of this operation also, the skins become considerably softened.

Fig. 12. Delivery End of Conveyor Dryer.

(Proctor & Schwartz, Inc., Philadelphia.)

Then if the pelts have not been previously oiled during the tanning process, or prior to the drying, they receive this treatment now. The oil or fat is applied to the leather side of the furs, which are then placed in the tramping machine for a short time in order to cause the oil to be forced into the skin. The fibres of the corium thus become coated with a thin layer of fatty material, which contributes greatly to the softness and flexibility of the pelt, and increases its resistance to the action of water, and also, in certain instances a partial chamois tan is produced, thereby improving the quality of the leather.

Fig. 13. Stretching Machine for Cased Skins.

(Reliable Machine Works, Evergreen, L. I.)

The skins are now returned to the work bench, and subjected to the stretching or “staking” process. This consists in drawing the skin in all directions over the edge of a dull blade, which is usually fixed upright in a post with the edge up. Or, the stretching may be done on the fleshing bench, substituting a dull blade for the fleshing knife. Recently staking machines are being used in the larger establishments, the work being done much more quickly and efficiently. As a result of this operation, the leather becomes very soft and flexible, every bit of hardness and stiffness being eliminated, and the skins receive their maximum stretch, thereby giving the greatest possible surface to the pelage. This not only helps to bring out the beauty of the hair, but is also a decided advantage from the economic point of view, as a considerable saving of material is effected in this way, sometimes even to the extent of twenty-five per cent. Cased skins are stretched in a somewhat different manner, by means of stretching irons. These consist of two long iron rods joined by a pivot at one end. The skins are slipped on to the irons, which are then spread apart, and in this way the skins are stretched and softened. A machine which does this work very efficiently is shown in [Fig. 13]. The skin is drawn onto the stretching arms, in this case made of bronze, which are then forced apart by pressing on a pedal. When properly stretched to the maximum width in all directions possible, and thus thoroughly softened, the skin can easily be reversed, that is, turned hair-side out. As many as 6000 skins can be stretched, or 4000 to 5000 skins stretched and reversed by one man in one day on such a machine.

Fig. 14. Fur Beating Machine.

(S. M. Jacoby Co., New York.)

The pelts are then combed and beaten. In smaller plants these operations are done by hand, but suitable machines are being employed. In order to straighten out the hair, it is combed or brushed. Then in order to loosen up the hair, and to cause it to display its fullness, the furs are beaten. This process is also done by hand in some establishments, but up-to-date places use mechanical devices for this purpose. A type of machine which has proven very successful, and is enjoying considerable popularity is shown in [Fig. 14]. These machines are also made with special suction attachments which remove all dust as it comes out of the beaten skin, thereby making this formerly unhealthful operation thoroughly sanitary and hygienic.