K. J. Adcock

The dressing and finishing of leathers of all kinds seems to be of growing importance every year, despite the fact that the durability of leather is often impaired by the chemicals and heavy machinery used in order to get a clear and bright colour or a highly-glazed finish. One exception to this rule, however, is japanned and enamelled leathers made by the new collodion-amyl acetate process, which not only produces the so-called "patent" finish, but also adds to the strength of the leather.

Dressing and finishing may be conveniently classified in four sections—

1. Finishing of boot sole leather.

2. Dyeing and finishing of machine belting, strap, harness, and other heavy greasy leathers.

3. Dyeing and finishing of boot, portmanteau, case, bookbinding, hat, and upholstery leathers, and of the numerous fancy leathers.

4. Dressing, dyeing, and finishing of glove and chamois leathers.

There are also a few special kinds of leather which do not come within the scope of this list. The limited size of this book makes it impossible to outline the finishing of all kinds of leather, and only a few of the important varieties can be referred to in the following pages.

Sole Leather

Formerly, the finishing of sole leather was a fairly easy matter, as the slow process of tanning with oak bark which was in general use gave the latter a nice fawn colour. The modern tendency, however, is to demand even lighter-coloured leather than that produced by an oak bark tannage, and, as most of the mixed tannages impart a darker colour, the practice of bleaching has been universally adopted. This process is to be greatly deprecated, since it reduces the strength of the leather. Further, it has the serious drawback of removing matters which would add to the waterproof quality of the leather, and yet the boot manufacturers demand light-coloured sole leather. As in many other articles of modern manufacture, quality is sacrificed for appearance. The colour of sole leather is of no importance whatever to the wearer of the boot, and the public should make a strong protest against bleached sole leather, and also against leather weighted with adulterants, if they wish to get boots of good wearing quality. It is difficult to know where the finishing of some of the modern sole leather begins. Formerly, the line of demarcation between tanning and finishing was distinct, for the finishing processes were begun as soon as the hides were sufficiently tanned. This is by no means the case to-day, as, in many cases, the finishing may be said to begin with a supplementary but unnecessary tannage in very strong tanning extracts, with the object of making the leather firm and plump, and, incidentally, imparting additional weight. This practice would be discontinued if sole leather were sold by superficial measurement. On the other hand, those who favour the continuance of the present system of selling by weight assert that the adoption of the measurement system would indubitably result in the production of a lot of under-tanned leather, that mechanical means would be devised to stretch the leather and thus give it an artificial area, and that a fair quantity of the leather produced does not lie flat, and would, therefore, be difficult to measure correctly. A great point in favour of selling by measurement is that there would be no necessity to weight the leather, and a mere visual examination would suffice to determine the quality, whereas it is often difficult to state whether leather has been treated with injurious artificial matters or not, and certainly impossible to determine the extent of this fraud, without a careful and somewhat elaborate analysis. Of course, there are some rough practical tests for ascertaining the quality of sole leather, especially in regard to the extent of its resistance to water. A weighed quantity of the leather is soaked in water for twenty-four hours, taken out, squeezed, dried, and reweighed. If the loss of weight does not exceed 5 per cent., the leather is a good sample and well tanned; on the other hand, it does not follow that a loss, say, of 40 per cent., would indicate adulteration with injurious materials, as the leather may have been tanned with an excess of strong extracts which have not properly combined with the fibres, with the result that the excess is easily removed in contact with water. However, methods of fixing tanning extracts on the fibres of the leather have been devised (see p. 117). A careful note should be made of the time required to soak the leather through; if water is absorbed rapidly, the leather is, naturally, unfit for soles.

After the tanner has taken great pains to produce the paleness of tint required, the shoemaker buffs away the grain, thereby reducing the resistance of the leather to wear, and then generally covers it with a black, tan, or white dressing. In its turn, this finish is likewise spoiled the first time the leather is worn. There could be nothing more futile than the elaborate finishing of sole leather to make it pale in colour, as it means that fully 80 per cent. of the leather produced has to be bleached in some way or other; and the manner in which this process is effected has a direct influence on reducing the wearing quality of the leather. If, for example, the colour of the leather is brightened with myrobalans, or sumach, or with extracts of these materials, the wearing quality is not affected; unfortunately, this method is not largely used, as it does not increase the weight of the leather and would tend to make it soft. A large proportion of sole leather is treated with strong sulphited extracts, which both bleach and increase the weight of the leather. In some cases, the leather is placed in vats containing hot tanning extracts to increase the bleaching effect and add to the weight. The gain of weight by this surplus tannage may be, and often is, from 8 per cent. to 10 per cent., and, whereas the tanner a century ago used to get only slightly above 50 per cent. of leather on the weight of the raw hide, it is no uncommon thing nowadays to get a yield of nearly 70 per cent.

The tanners are hardly to be blamed for this practice, which really ought to be stopped; it is almost entirely due to the demand of buyers for leather at a low price per lb., irrespective of its superficial area compared with a higher-priced and often cheaper article. It is only fair to state that those boot manufacturers who have taken careful costings of their leather have not suffered great loss in this way, but most repairers buy common leather in order to be able to do their work at fixed prices usual in this trade. A large proportion of this leather is under-tanned or weighted, and, in either case, absorbs water like a sponge. This kind of leather is quite unfit for soles, and ought to be condemned, as it not only absorbs moisture but also retains it for a long time, so that it is frequently a cause of colds and other complaints arising from chills. If the repairer does not cost his leather as accurately as the wholesale boot manufacturer, the latter often neglects to take into account the quality of the leather, so long as cheap soles can be cut from it.

The continual demand for leather which will yield low-priced soles has brought about another practice which is much worse than the use of hot extracts. In this case, the hides are not tanned thoroughly, but, instead of completing the process with tanning extracts, the leather is treated with cheap chemicals, such as epsom salts (magnesium sulphate), glucose, and barium salts. These add considerable weight and save the cost of expensive tanning materials; further, it is claimed that they give increased firmness and substance to the thinner parts of the leather, which otherwise could not be used for soles. It is conceivable, therefore, that leather of this kind could be cut to greater advantage than that properly tanned, but, since this artificial filling is washed out on the first contact with water and the leather rapidly deteriorates through attracting and retaining moisture, the fraud of the system is at once apparent.

Although the use of leather artificially weighted with hygroscopic chemicals is extremely detrimental to health, it was only during last year that laws were passed forbidding the adulteration of leather, and even these are inadequate. Strange to relate, the two countries where these legal measures have been taken, Australia and South Africa, enjoy for the most part a hot and dry climate, while it is in wet weather that adulterated leather is most harmful. However, to Australia belongs the honour of initiating legal measures against frauds in leather manufacture, and their praiseworthy action must soon be copied by other civilised countries.

On the other hand, it would be inadvisable to prohibit the addition of every other material except those with tanning properties. There are undoubtedly a few substances which, used in combination with the tanning materials, add to the strength and value of the leather, and it is the opinion of some tanners that great developments will take place in this direction. Certain oils, sulphonated in order to render them easily miscible with water, and known commercially as "soluble" oils, exercise a beneficial effect when mixed with the tan liquors, for they lubricate the fibres of the leather, assist penetration of and fix the tannin. The time required for the process is, therefore, much reduced, as strong liquors may be used without harmful effect. The oil also serves as a lubricant for the fibres, obviates the harshness and brittleness usually associated with rapidly-tanned leather, and fixed to the extent of about 3 per cent., must increase its durability. Best of all, from the tanner's point of view, there is a moderate increase of weight. There are two or three special tanning oils on the market.

A vegetable gummy product has lately been introduced to the trade which has been found to give remarkable results when used in conjunction with tanning materials. This gummy matter is extracted from vegetable seeds and is placed on the market under the name of Tragasol. Its composition is somewhat similar to that of tannins, the Tragasol Co.'s analysis showing it to contain 43.51 per cent, of carbon, 6.23 per cent. of hydrogen, 48.38 per cent. of oxygen, 0.39 per cent. of nitrogen, and 1.49 per cent. of ash. It is very largely used for strengthening and sizing textile fabrics, and seems destined to play an important part in the leather trade, for it has tanning properties, increases the strength of the leather, and considerably hastens the process. Its most important advantage is that it permits successful tannage in the drum, thus effecting a great saving of time and labour.

Hitherto, rapid tannages have not been very successful, as they generally made the leather harsh and brittle, and lessened its durability. Leather tanned by previous rapid methods was also less waterproof than that tanned in pits by slow methods. All these defects are avoided by using Tragasol, which, when combined with tanning extracts, forms a curdy precipitate, described by the makers of Tragasol as cutiloid (contraction of cutis and colloid, cutis meaning "skin," and the Tragasol being, chemically, a colloid). The cutiloid tannage increases the water-resistant properties of leather, and prevents the oxidation and consequent darkening of the colour of the tanning material used with it. Tests have been made which show that cutiloid-tanned leather will withstand a fall of water 12 in. high for six weeks before complete penetration takes place; ordinary tannages do not often resist water for more than a few hours.

For the tannage of sole leather in the drum by the cutiloid process, about 120 per cent. of Tragasol and 40 per cent. of chestnut or oakwood extract are required; this quantity is divided into four equal portions, which are added to the drum successively at intervals of one hour. The hides should then be nearly tanned through, and the process is completed with strong extract (chestnut and quebracho, or myrobalans, according to the kind of leather required). After drumming the hides for ten hours, they should remain at rest for two hours, then drummed another hour, and so on, alternately, until the completion of the process, which may require from twenty-four to thirty-six hours, according to the substance of the hides. By this process, the yield of leather may exceed 60 per cent. of the weight of the raw pelts. This percentage of yield may be raised to 70 per cent. or more in the case of sole leather by steeping the hides in hot extract.

The action of acids in swelling gelatine is sometimes abused, particularly on the Continent and in America. As pointed out before, tan liquors must be mildly acid in character before the process can proceed, and, if the organic acids of the tanning materials are insufficient, the addition of a small quantity of formic, or lactic, or acetic acid is necessary; but, in many of the American acid tannages, an excessive quantity of mineral acid is used, with the object of swelling the hides. When in this condition, they rapidly absorb an abnormal quantity of tannin, and the finished leather is unnaturally thick. To make matters worse, the tannage is sometimes not completed, but, instead, the hides are treated ("doped") with hygroscopic chemicals, which not only increase the weight of the leather but also endanger the health of those who have to wear it. Most of the American tanneries make no secret of their use of these unnecessary chemicals, but assert that they are obliged to use them in order to meet competition, and because a large number of bootmakers insist on buying sole leather at a low price per lb. The Leather and Paper Department of the U.S.A. Bureau of Industry analysed several American leathers in 1913 and found that a large majority were artificially weighted with glucose and Epsom salts (magnesium sulphate). Barium compounds are also used for the same purpose, but the American tannages are apparently free of this adulterant. The results were published in a pamphlet by the United States Government, together with a list of the firms whose leathers were tested.

While the European tanners do not weight their leather so freely as the Americans with these chemicals, the practice of swelling the hides unduly is not unknown, with the difference that, especially on the Continent, the swollen fibres are fixed by treating the hides with a weak solution of formaldehyde, which also acts as a preliminary tanning agent. The tannage can then be rapidly completed with fairly strong extracts, as the formaldehyde prevents the contraction of the grain which would ensue if untreated raw pelts were placed in strong tan liquor. The acid-formaldehyde process is risky, and cannot be recommended. The use of the artificial tannin, neradol, has replaced it in many Continental sole-leather tanneries. A preliminary tannage with neradol forms a good mordant for the use of the strong extracts.

Fig. 26

PINNING SOLE BUTTS

Whatever the method used to improve or depreciate the natural tannage, the surplus material left on the surface is raised or brushed off, and, after the leather has been left to drain for a few hours, it is sent to the finishing department, which is usually the drying shed. There, it is left piled up for a day or two, until it is in the right condition for oiling. The leather must be oiled, otherwise the grain would be harsh and brittle when dry, and would darken in colour, especially at the edges. Cod oil is generally used, and sometimes a little mineral oil is added to it to prevent possible impurities in the fish oil rising to the surface of the leather or causing damage in other ways. A cod oil purified by distillation would, however, be quite safe to use, and there seems to be no reason why tanners should use crude oils so frequently as they do, now that a large number of oils specially prepared for the leather trade are available. Linseed oil is also used in admixture with cod oil, its oxidising properties hastening the process of drying. The leather is liberally oiled with a brush or swab on the grain side and immediately hung up in the drying shed, where it is left until it reaches what is technically known as a "sammed" condition (i.e., just damp enough to exude no water when the leather is doubled over). It is then struck out ("pinned") on the grain side, either with a hand tool (Fig. 26) or by machine. In the former case, the leather is placed on a long wooden beam and the pinner works from the left side, keeping two of the three edges of his knife flat on the leather while making heavy forward strokes. As the scum is worked out, the operator mops it up with a wet cloth. Machinery has replaced hand labour in this operation in all modern tanneries. The pressure of the tool removes scud and dirt, varying in quantity according to the amount of "bloom" contained in the particular tanning materials used. The leather is then laid in pile for a few hours, when it is in a fit condition for the first rolling, which is known in the trade as "rolling on." This operation is generally done by machine (Fig. 27) nowadays, but the old method of using a hand roller heavily weighted with an iron box (Fig. 28) is still practised in a few yards. After rolling, the leather is hung up again until nearly dry, when it is taken down and sized with a weak colouring matter, made up of annatto or tumeric, with chalk or whitening dissolved in white vinegar (acetic acid) and diluted. It is then rolled again ("rolling off") and polished with a piece of flannel. Finally, it is hung up to air off, and is then ready for the warehouse.

In many yards the finishing consists merely in striking out the leather, rolling it when properly tempered, hanging up until nearly dry, and re-rolling. An American machine for giving the final polish to sole leather has lately been introduced.

Instead of the rolling machine, some French tanners use the hammering machine, which gives good results, but is necessarily slow and frightfully noisy in action. The steel hammer moves up and down with remarkable rapidity, but only a small area is covered by each blow.

The artificial drying of sole leather, or of any other kind, is a matter that needs careful attention, for it is obvious that great delay would occur, and a large amount of business would be lost, if tanners relied solely on the climatic conditions of the British Isles; in fact, the weather is so rarely fit for drying leather that every up-to-date tannery contains some artificial aids, the need for which has been more pressing since a large proportion of leather contains a surplus of tanning matter which is liable to oxidise in contact with strong light and air, thereby darkening the leather and making it brittle.

Among the satisfactory drying plants are those of Howard-Smith & Co., and the Sutcliffe Ventilating and Drying Co., Ltd. Both work on the theory of fanning a continuous current of hot air through the drying-room, so that the moisture evaporating from the leather is constantly drawn off while the apparatus is at work.

The Howard-Smith plant consists of a series of steel tubes into which hot water or steam is pumped. These pipes are enclosed in a chamber in which the air naturally acquires great heat. A fan (Fig. 29) is fixed in one side of this chamber (Fig. 30) and, when in motion, drives the hot air through a wide tube which leads to the drying chamber.

Figure 31 shows the Sutcliffe Fan and Heater installed in a tannery. At least two hygrometers should be hung up in a drying-room to determine the amount of moisture in the air.

Chrome Sole Leather

The manufacture of chrome sole leather suitable for ordinary walking boots is of comparatively recent origin, although natural chrome hides were dressed more than twenty years ago for tennis boot soles and other athletic shoes. There can be no doubt of the superior wearing and waterproof qualities of well-dressed chrome sole, but its high price, compared with that of vegetable-tanned sole leather, is against its general use.

Either the one bath or two bath tannage (described on p. 108) may be used, but, on the whole, the one bath method is preferred for the following reasons: (1) Its application is easier; (2) it produces a firmer and less elastic leather; and (3) there is practically no danger of weakening the hide fibres. On the other hand, the two-bath process produces a plumper leather which can, naturally, carry more dressing and command a correspondingly better price. In skilled hands, it is also under better control than the one-bath process, while it is absolutely necessary for the popular pale bluish-grey tint of chrome leather tennis soles.

The natural chrome sole requires very little dressing. The chromed hides (usually rounded into butts or bends, shoulders and bellies) are allowed to remain on a horse two or three days after the completion of the tannage, so that the oxide of chromium may combine more firmly with the fibres. They are then placed in the drum tumbler again and washed in cold water for several hours. A constant stream is conveyed to the drum through a rubber pipe fixed to the tap, and escapes through small holes in the drum. The acid salts are not thoroughly removed by this washing and must, therefore, be neutralised with an alkali. Borax is the best for the purpose, owing to its mild action on leather and antiseptic properties. From 1 to 2 per cent. borax on the weight of the leather is generally sufficient, while, if soda be used for economical reasons, only half the quantity is required. The drum is revolved for about an hour; the liquor is then run off, and the leather receives a further washing in cold water for half an hour, when it is in a condition to receive the dressing, which is chiefly composed of materials which help to fill and lubricate the interstices of the fibres so that the substance is maintained and the natural strength of the fibres preserved. Gelatine, pure glue, Tragasol, paraffin wax, carnauba wax, spermaceti, Marseilles soap, are among the various ingredients used; while the delicacy of the tint may be improved with china clay or French chalk. Recipes vary considerably, each manufacturer claiming to have secret methods. Solutions are made of the ingredients, or, where one or more of the materials are insoluble, they are atomised in a mixing pan before use. To induce thorough penetration, the dressing liquid may be applied to the leather at a fairly high temperature, as chrome leather is unaffected by heat which would destroy the fibres of ordinary vegetable-tanned leather. Even so, it is inadvisable to use a higher temperature than 170° F. The leather is thoroughly impregnated with the dressing in about an hour's time, and is then piled on a wooden horse for several hours, or overnight, to drain and permit thorough incorporation of the dressing with the leather. When well-drained, the grain of the hides is smoothed by pressure with a special tool (Fig. 32) or by machine, the operation being known technically as "striking out." The machine (Fig. 34) gives quite satisfactory results and has replaced hand labour in all modern works. The hides are then "strained" (i.e., extended and nailed to wooden frames), or they are simply hung up to dry. In the latter case, there is a small shrinkage of the size of the hide, but the substance is maintained. With good straining, a satisfactory increase of surface measurement can be obtained.

When the leather is completely dried, it may be sold at once, but if, as is generally the case, a special "nap" finish is required on the flesh side, the hides are placed in damped deal sawdust until they are in the right condition of flexibility for the next process, known as "fluffing." This is done on a rapidly revolving wheel (Fig. 33) covered with emery powder varying in the size of grain according to the effect desired on the finished leather. The abrasion of the leather on the flesh (i.e., the under side) raises a soft nap. Carborundum, a special abrasive made in America, by the fusion of sand, coke, and salt at a very high temperature, has to some extent supplanted the use of emery. As a final finish, the flesh side may be rubbed over with chalk or china clay to give it a clear saleable appearance.

The chrome sole leather used for ordinary boots is quite a different product, and it is only in the last two or three years that it has been used to any extent. The "Dri-ped" is the best known make of this leather. The tannage is effected by the one or two-bath methods already described. The processes preparatory to chroming are very important, as it is essential to get the maximum yield of pelt. The hides are, therefore, often treated with sulphide of sodium, which loosens the hair in twenty-four hours or less. They are then placed in fairly strong limes for two or three days to swell the fibres and saponify the grease. After being washed in cold water, the hides are treated with a weak solution of lactic, boracic, or butyric acid, or butyrate of ammonia, to remove all trace of lime, when they are ready to be chrome-tanned. After chroming them, neutralisation of the acid chrome salts is effected with borax, and the leather is ready for dressing. The principal objects of this process are to make the leather firm and waterproof, and to remedy its tendency to slip easily on wet pavements. The last-named is the greatest difficulty, and there are only about two or three firms who have really surmounted it. Each manufacturer keeps his recipe secret, but the ingredients that go to make the various dressings are drawn from the following: Stearines, mineral oil, Tragasol, resin, carnauba wax, beeswax, paraffin wax, glue. Resin, or asphalt, or both, may be used to prevent the leather slipping in contact with a wet pavement. One patent describes a method of dressing chrome sole leather with a mixture of asphalt, resin, and paraffin wax.

The waterproofing ingredients are preferably applied to the leather in the tumbler at a high temperature, say, 160-170° F. After running the drum for about three-quarters of an hour, the leather is impregnated with the mixture, and is then horsed up for at least twenty-four hours to allow complete incorporation of the fatty ingredients with the fibres of the leather. A suitable waterproof dressing and filling increases the strength of the leather.

The finishing of the leather is simple. The butts or bends are smoothed and stretched out by machine (Fig. 34), oiled on the grain, nailed or extended with special metal grips on square wooden frames, and dried. In some cases, they are hung up until nearly dry, rolled by machine instead of being put on boards and aired off in a drying stove.

A patented method of making waterproof chrome sole leather to prevent it slipping and losing its shape in wear consists in first treating the leather in a solution of glue, gelatine, agar-agar, or other colloidal substance, with the addition of formaldehyde, and then submitting it to strong pressure under the influence of a high temperature, in order to fix the colloidal matters. The pressure is made between heated plates. The leather is afterwards impregnated with a mixture of wool-grease, pitch, asphalt, resin, wax, gutta-percha, etc. A recipe given in the specification consists of wool grease (60 parts), asphalt (10 parts), soft pitch (25 parts) and gutta-percha (5 parts). The mass is fused and kept at 90° C. The hides are placed flat in this mixture, which they quickly absorb.

If the British Government should ever introduce a Bill to stop the adulteration of leather, it may be found somewhat difficult to deal with chrome sole, which must have some filling material to make its use practicable. No exception can be taken to the dressing of leather with materials that make it waterproof and increase its strength; in fact, much more will be done in this direction than has ever been attempted in the past, as waterproof sole leather is a necessity in Great Britain. Any measure to check the adulteration of leather must, therefore, clearly define the chemicals which are known to be harmful in leather and which may not be used. This has not been overlooked by the Australian Government, which has forbidden the use of barium salts in leather, and likewise the importation of leather boots or any goods made of leather containing this chemical. Such goods sent to Australia are liable to confiscation, and it is reported that a few consignments of boots have already been condemned.

Leather, either exported or imported, must not contain more than 3 per cent. of glucose unless the percentage is marked on each consignment, in which case, it is presumed, a tanner may use as much of the adulterant as he likes, although the fact that he has to disclose this practice acts as a deterrent in most cases. Unfortunately, the Australian Act leaves an important loophole, since the use of Epsom salts, which can be made to increase the weight of leather more than any other chemical, is not prohibited. In any case, none of these hygroscopic materials is of any use to chrome sole, for they would attract moisture which it is desirable to resist.

Vache Sole Leather

As its name implies, vache sole leather is a Continental product, being made chiefly in France, Belgium, and Germany. The raw material consists of light and medium cow hides. The details of working are somewhat similar to those used in tanning English sole leather, the main difference being that the hides are suspended in the lime liquors instead of throwing them in flat. The system of tannage is not so varied as the English, since the materials used generally consist of oak and pine barks, myrobalans, quebracho and oak extracts; and the finishing materials are of quite another character. The Continental tanners generally use the RÉaumur thermometer, while the BeaumÉ hydrometer is used to determine the density of the tan liquors in place of the English barkometer (Fig. 24). One degree BeaumÉ is equal to 6.9° barkometer.

Vache leather is more pliable than English sole leather, but the addition of valonia extract towards the end of the tanning process would greatly increase its firmness.

The finish is applied to the flesh side of the leather, and a typical recipe consists of a size such as Irish moss or Tragasol (1 part), flour (20 parts), china clay (20 parts), and pure gambier (2 parts) in 200 parts of water. The size is dissolved and cooled, and the other ingredients are then added.

Machine Belting, Harness, and Saddlery Leathers

These leathers are rarely made by one firm; usually, strap butts and most kinds of belting leathers are dressed by curriers, whose trade is quite distinct from that of currying shoe leather. The tanning and currying of harness and saddlery leathers is another special branch. Besides these three important trades, there is the dressing of hydraulic, mechanical, and other industrial leathers, which likewise form special sections of the heavy leather industry.

Belting leather is an important item in the trade, and, as a good proportion is made from the finest hides, this class of leather is among the most expensive made. At present, there is much controversy in the trade as to whether the vegetable-tanned or the chrome-tanned article is the more economical in use. Briefly, chrome belting is superior in works where there is much steam or mineral acids, as it is not affected by these conditions to the same extent as bark-tanned belting. Its tensile strength is also greater, but against these advantages must be set its higher cost and tendency to stretch unduly in comparison with the vegetable-tanned product. It can be safely said, however, that the use of chrome belting is on the increase, although its production is not nearly on such a big scale as that of the old type of belting.

The tannage of belting leather is similar to that of sole leather, except that there is no necessity to continue the process, after the tannin has struck through, with the object of increasing its firmness and weight. Attention must also be paid to the class of tanning materials used, especially for belting of the best quality, as it must have great tensile strength and stand a severe strain in the dynamometric test. Tannins that rapidly oxidise in contact with light and air have, therefore, to be avoided. The oak bark tannage, with a little chestnut and oakwood extracts to finish the process, is a good method of imparting to the hide the right degree of firmness and flexibility.

As in the case of sole leather, belting may be artificially weighted during the tannage, although it is usually done in the currying process, if at all. There can be no doubt that a quantity of adulterated belting leather is made, and will continue to be made while the practice of selling by weight is in vogue. As a rule, sophisticated belting leather has a much weaker tensile strength than the pure product and is of relatively poor value, since the reduction of price is usually a matter of only a few pence. If users of belting bought on the principle of value instead of price, they would never buy adulterated leather.

In tanning hides for belting, the shoulders and bellies are cut off and usually dressed for sole or harness leather, leaving the butt, the prime part of the hide, 4-1/2 ft. in length (Fig. 23). The tanned butt is first shaved to level the substance, then washed in a solution of borax, and sumached in the drum. After smoothing the leather in the striking-out machine, it is partially dried ("sammed") and then rubbed on both sides with a dubbin of cod oil and tallow. In this condition the butts are left piled up for a few days, so that the dubbin penetrates the leather, which is then extended with the sleeker (Fig. 32) to make it smooth and to remove surplus grease, which is sold to soap-makers under the currier's name of "moisings." The leather is finally dried, rolled (optional), stretched by machine, and cut up in the width of belting required. Instead of "hand-stuffing" the leather with cod oil and tallow, which is still the best method, a large quantity of butts are now "drum-stuffed," the object being to make use of stearines, which are harder and heavier greases than tallow. The type of drum shown in Figure 35, in which the grease is incorporated with the leather by means of live steam, gives satisfactory results, although hot air apparatus is now replacing the steam injector.

A patent has lately been granted to an American inventor for the production of a strong and cheap belting. Flesh splits of hides are simply stuck together with a collodion or nitrocellulose solution. Any number of layers may be used, according to the substance required, the only essential quality being that the leather should be free from grease. The adhesive property of nitrocellulose solutions is probably stronger than that of any other material, but, unfortunately, the tough film they form on drying does not grip a greasy surface. Before the solution used to join the pieces of leather together is dry, the leather is rolled under heavy pressure, and, when thoroughly dried, can be cut up for belting.

The dressing of harness leather is similar to the manual process of making belting, with the exception that the butts or bends (half butts) are stained either black or a pale straw colour, the latter being known to the trade as the "London colour." Annatto is often used to get this colour. The bright, greasy finish on harness leather is obtained by rubbing buck tallow over the grain and polishing with a glass sleeker or a piece of flannel. The operation is sometimes done by machine, in which the working cylinder is covered with pieces of cotton rag.

Saddlery leathers are dressed on similar lines, but the finish is not so greasy as harness. Pig skins make the best and toughest leather for this purpose. They are dressed in a similar manner to harness hides, but special attention has to be given to pig skins to get rid of the large quantity of natural grease they contain.

Boot Upper Leathers

Whereas the number of different kinds of boot upper leathers in use less than three decades ago was limited to five or six (waxed calf, calf kid, French kid, mock kid, levant, coloured calf) it is now almost legion. Although the variety is almost bewildering, however, the popular demand is confined to about half-a-dozen sorts, which include real and imitation box calf, box hide, glacÉ or glazed kid, patent leather, willow calf, dull-finished chrome leather, and waxed kip butts and waxed splits for workmen's boots.

Box leathers and glazed kid are the most popular of all. Generally speaking, glazed kid is more suitable for wear in the summer and autumn; while box leather, being thicker and stronger, is preferable for the winter. Imitation willow calf (i.e., calf skin tanned in vegetable and chrome liquors, either separately or combined) is very suitable for easy-wearing boots, but is not so durable and resistant to water as the pure chrome-tanned article.

The tannage of box and willow leathers may be effected by the one or two-bath process already described (p. 108). Before the tannage, it is advisable to pickle the hides or skins in a solution of alum and salt, with the object of preventing contraction of the tissues of the hide, and providing a mordant for the more rapid absorption and fixation of the chrome salts. The tannage completed, the acid salts in the leathers are neutralised with borax, and after the leather has been washed in warm water it is ready for dyeing. The dyeing of box calf is generally done in the drum tumbler, but there are several other methods. One system used on the Continent is to dip the skins, a pair at a time and placed flesh to flesh, in a very strong dye liquor. This method is slow, and not in accordance with modern ideas; used for producing browns and fancy shades, it is very difficult to avoid irregularity of colour where large parcels are manipulated. Another method is vat dyeing, the process being carried out in a wooden vat (Fig. 25) and the dye liquor circulated by means of a paddle. The one advantage of this system is that the leather can be easily examined during the process. A useful method of dyeing is carried out by brushing the colouring materials on the grain side of the leather. This process is economical, and it has the further advantage that the finished leather can be used for unlined boots and other purposes where an undyed flesh is necessary.

The original "box" leather was dyed a dark-blue shade in the drum before it was shaved, and, as the dye does not penetrate very far into chrome leather, unless a strong mordant of tannin be previously used, the subsequent shaving left the flesh side of the leather a very pale-bluish tint.

The process of dyeing is least troublesome and most effective when done in the drum tumbler. The leather is run in warm water until the temperature reaches 140°-150° F (60°-66° C.) and the dyeing materials are added gradually in a box at the side of the drum whence it passes through the axle or journal into the tumbler. Although chrome leather is not materially affected by boiling water in contradistinction to vegetable-tanned leather, which cannot be treated with water above 60° C. without injury, it is inadvisable to dye it in boiling solutions, the above-mentioned temperature being the most satisfactory. There are two methods of dyeing blacks in the leather trade: (1) the logwood-ammonia, and (2) the aniline black. The former is the cheaper of the two and quite satisfactory, although many dyers seem to prefer the aniline process. The latter certainly gives a deeper black, but it is not at all necessary to make the flesh side of box calf black, and many buyers prefer the back blue, although, of course, the grain side of the leather must be finished a jet black. The crude logwood is generally subjected to a process of fermentation or "ageing." The new wood has to be placed on stone or cemented flooring in a warm room and frequently turned over until fermentation has ceased, which usually takes about a week. It is then cut into small chips by machinery and packed in bags. This is the form in which it always used to enter the tannery, but it is now generally prepared in paste or crystal extract by makers of tanning and dye-wood extracts, a business which grows in importance every year. The colouring matter of logwood is haematoxylin, which is converted into haematin by oxidation; hence, the extract is often referred to as haematin crystals. The paste may be used where it is desirable to increase the substance of the leather, but most dyers prefer the crystals, which are easily dissolved in hot water. One lb. of crystals, to which is added just enough ammonia to change the brown colour to violet blue, suffices for each 100 lb. of leather dyed. The colouring matter is absorbed by the time the drum has been running half an hour, leaving clear water behind. The next process is known technically as "fat-liquoring," which, as its name implies, consists in lubricating the fibres of the leather with fatty or oily matters. This is a very important process, for, when suitable ingredients are used, the pliability, strength, and waterproof quality of the leather are greatly increased. The making of special fat-liquors for different kinds of leather has become quite an important business, and most makes can be depended upon for the specified purposes. It is a debatable point as to whether fat-liquoring should precede or follow dyeing. Generally speaking, it is better to adopt the latter course, as the fatty ingredients help to fix the colouring matter on the fibres of the leather. The dye is also less liable to fade when fat liquoring follows the colouring.

The number of materials that may be used for the process of fat-liquoring is almost legion, but the principal are soaps, oils, egg-yolk, tallow, flour, Tragasol, Irish moss, china clay, and starch. Unless the special preparations made by leather trade chemical firms be used, much care has to be exercised in selecting the most suitable ingredients for each class of leather. For example, the mixture that would give good results on vegetable-tanned leather might be quite unsuitable for chrome leather. Then, again, the selection of material is based on the style of finish required, a dull finish necessitating heavy fats and greases which would be quite unsuitable for bright leathers, and particularly for those of the chrome-tannage. Among the hundreds of recipes that have been published from time to time, tallow has only found a place in one or two mixtures, yet it is one of the finest materials for strengthening and lubricating the fibres of leather. If its splendid properties were fully known, it would be very largely used for fat-liquoring purposes. Of course, it is well known to the currying trade, having for several centuries formed the basis, together with cod oil, of the dubbin used in stuffing waxed leather and belting butts.

The following is a useful recipe for a fat-liquor for box calf: 2 lb. Marseilles soap and 3 lb. neatsfoot oil for every 100 lb. of leather. The soap is cut into small pieces and dissolved in hot water, and the oil is added slowly and thoroughly mixed by stirring vigorously. Where possible, emulsification should be done in a machine, in order to atomise the ingredients. The finer they can be brought into a state of division, the better they will be absorbed by the leather. Other suitable fat-liquors for box leathers are the following: (1) Turkey red oil, 2 per cent. of weight of leather and neutral soap 1 per cent.: (2) neatsfoot oil, 2 lb.; tallow, 1 lb.; and Tragasol, 1 lb.: (3) cod oil, 2 lbs.; Marseilles soap, 1 lb.: (4) neatsfoot oil, 2 lbs.; egg-yolk, 1/2 lb., or six fresh yolks. The process is completed in 20-30 minutes.

In the case of fancy colours or browns, the leather should generally be well-drained and warmed up again in the drum in hot water (170° F.) before fat-liquoring, but the precaution is unnecessary for black leathers. After the fat-liquoring process, the leather is removed from the drum, and piled up on the horse to drain, and left for several hours or overnight, to allow it to assimilate the fatty ingredients. It is then submitted to an operation known as sleeking or striking out, with the object of removing surplus water and so facilitating drying, and making the grain side smooth. Machinery is now almost universally employed, especially for chrome leather. A good type of striking out machine is shown in Figure 34.

If done by hand, the skins are placed on a sloping glass or slate table, with the flesh side uppermost, which is then stretched out by strong pressure with a tool known as a sleeker, the strokes being made downward in the direction of the hair growth. The flesh side done, the whole skin is turned over and the grain side is similarly treated. Sometimes only the flesh side is struck out, especially if the grain is soft and tender. The sleeker consists of an iron, steel, or copper blade, about 6 in. square, fitted in a wood handle (Fig. 32). The skins are hung up in the drying-room immediately they are extended and smoothed by sleeking, and are then either allowed to dry completely, or, as is generally the case with best leather, they are hung up until a great deal of the moisture is evaporated and the skins are left in a slightly moist, or, as it is generally termed, "sammed" condition. The skins are then taken down, damped in dry parts, folded over, laid in piles to equalise the moisture, and finally smoothed out and stretched again by hand or machine. This second operation after the dyeing is known as "setting."

Chrome-tanned skins are usually stretched and nailed on square boards after setting, as, owing to their elasticity, they are liable to shrink considerably in drying. The superficial area can be increased by fully extending the skins. This operation is technically described as "straining." It may be stated here that vegetable-tanned leathers are not generally "strained" on boards, as such leather is better in quality and substance when hung up and dried. Leather of combined tannage (i.e., tanned with vegetable and chrome products) is, however, frequently "strained," as the astringent property of chrome would otherwise cause contraction of the fibres.

When dried on the boards the leather is somewhat stiff, and has, therefore, to be softened before any finishing ingredients are applied. Chrome leather is softened by placing it for a few days in damp sawdust, which, for brown or fancy coloured leather, must be of deal or white pine, and, therefore, free from objectionable colouring matter; but, for black leather, the sawdust of any wood is suitable. The skins must be systematically piled one above the other, and a little damped sawdust scattered over each skin.

When properly "seasoned," the skins are brushed free of the sawdust and "staked," either by hand or machine, usually by the latter means. The staking knife may be fixed in a wood crutch (arm stake), or fixed upright in a vertical wooden stand (knee stake). In the former case, the skins to be staked must be secured in a horizontal wooden groove fixed to two uprights, the workman then pressing heavily in a downward direction with the staking knife, of which the crutch is held under the armpit. In using the upright stake, the leather is moved to and fro over the edge of the fixed knife. Both of these manual operations are arduous and somewhat dangerous, and should be displaced by machinery wherever possible (Fig. 36).

The thoroughly softened leather is then dried, mordanted with a solution of logwood, or haematin crystals, blacked with levant ink, a specially prepared black dye, or with a suitable aniline dye, and dried again. It is finally seasoned with a glutinous or albuminous mixture (blood albumen, milk, and a little aniline black dye make a good mixture), dried, glazed, seasoned a second time, and reglazed. A light coating of mineral oil turns the finish into a jet black, and the leather is ready for the warehouse. There are several types of glazing machines, but the "grasshopper" (so called owing to its action) is the most popular for box calf. This machine is the same as shown in Figure 36, except that the working tool is replaced with a smooth glass or agate roller.

The term "box" applied to this leather was invented by a prominent American tanner, and had he registered the name and patented his process he would have reaped a very rich harvest, for the leather is used in enormous quantities throughout the world. As it was, the American firm tried to obtain an injunction against English firms manufacturing the leather, but had to withdraw their claim, as they were not the inventors of chrome leather, which was made in Scotland before it was introduced to the States. Moreover, the word "box," as applied to leather, was not registered in the United Kingdom.

Willow calf is exactly the same kind of leather as box calf, except that it is dyed brown instead of black. The seasoning mixture naturally differs and may consist of a mixture of egg albumen, milk, and a little of the same, or similar, dye solution as that used in the dyeing process. In order to get clear colouring, the dyes should be well dissolved and strained through fine muslin.

Chamois Leather

This kind of leather is well known to the general public under the name of wash-leather, but it is, perhaps, not so widely known that there is practically no real chamois leather available, since the species of animal bearing this name is almost extinct. Nowadays, "chamois," or "shamoy" is made from the flesh split of sheep skin, and the method whereby the leather is produced is described as the oil tannage. The chamois leather dresser may also do the preliminary work of fellmongering, but more often he receives the pelts, or "fells," from the fellmonger. Although the pelts have been in a lime liquor known as the fellmonger's "gathering limes," the process of liming has to be continued and carefully regulated. Too much liming makes the pelts loose, owing to the development of bacteria. This effect would cause the finished leather to be soft and spongy. On the other hand, under-liming fails to remove sufficient of the cement substance which binds the fibres of the pelts; consequently, the leather produced from these pelts is thin and somewhat gristly. After being limed, the skins are "cobbed" (i.e., the bits of wool or hair left on by the fellmonger are removed) and the pelts are then fleshed by machinery. The next operation, splitting, is very important and requires skilful attention to get good results. The Reeder machine is largely in use, but the band-knife machine is also suitable. The top half of the sheep skin (i.e., the grain side) is utilised for the manufacture of skivers, while the under portion, or flesh side, technically called "lining," serves as the raw material for chamois leather. The best linings are generally sorted out for making into parchment, which, of course, commands a much higher price than chamois. Linings for chamois are then submitted to the operation of either re-splitting or frizing, the object being to remove the loose tissue lying between the grain and flesh. The pelts are re-split in the case of cheap chamois, but frized if intended for choice finish. Frizing is an operation peculiar to the making of chamois and glove leather. It is done with a very sharp knife, similar to the fleshing knife, and on a more upright beam than that used by tanners. The work requires great skill, frizers being among the best paid workers in the trade. Frizing done, the linings are freed from lime by washing them in the drum tumbler, or paddle-vat, through which cold water is allowed to flow continuously for two or three hours. When lamb skins, which are too thin to split, are made into chamois leather, the grain is removed by frizing.

A quick and effective method of deliming is to treat the skins in a weak solution of lactic acid. Some dressers use a drench of pea-flour or bran. The mild acids produced by the fermentation of these materials not only neutralise the lime but also reduce the gristly nature of the skins to a soft, supple condition. The bran infusion is slightly warmed to hasten the process of fermentation, but the temperature must not exceed 100° F. (32° C.). The linings are then rinsed in cold water and sent to the stocking machines, in which they are kneaded until they become quite soft. Either the faller-stocks or the mechanical pushers (Fig. 14) may be used, the latter being the more modern machine. The operation may require from four to ten hours, the completion being determined by the condition of the skins. "Samming" follows stocking, and for this purpose the linings are hung up in the drying shed until thoroughly dripped, but not dried. In this slightly damp condition they are then prepared for the next process of oiling, which is the most important part of chamois-dressing, as it converts the perishable raw linings into leather. In the United Kingdom, cod oil (generally Newfoundland) is used exclusively, and gives best results. Whale and shark liver, or menhaden oils are often used abroad. The linings are placed in a tub or vat, a few at a time, and oil is poured over each layer until a sufficient number has been treated to fill the stocking machine. The stocks are run for half-an-hour, or until the oil has penetrated the linings, when they are put back into the vat, where they remain for about an hour. They are then re-stocked, taken into the shed to samm, re-oiled in the vat, and stocked again. These processes are repeated until the skins are thoroughly impregnated with the oil, when they are dried in a warm stove. The skins are not yet converted into leather, which only occurs in oil-dressing, after the oxidation of the oil. This is effected by spontaneous heat, the dry oiled skins being heaped in boxes and covered. Strict attention has to be paid to avoid over-heating the skins, which are turned over and changed at intervals. When the leather ceases to heat, the process is completed. It is then dipped into hot water and mechanically pressed, to remove surplus or uncombined oil, which is collected and sold under the name of "sod oil." The leather is afterwards drummed in warm water and finely cleansed in an alkaline solution, potash, soda, or borax, chiefly the first named, being used for this purpose. They are then rinsed in water, dried, damped, and softened by staking. At this stage, the best skins are sorted out for the glove makers. The others are finished for wash-leather by re-staking, paring with the moon-knife, and smoothing both sides of the skin with a scurfer, or fine pumice-stone. In the warehouse, they are damped, stretched out, piled up, and kept fully extended by placing heavy weights near the edges of each pile of skins.

Gloving Leather

Progress in the art of making leather for gloves has been rapid during the last few years; but further important developments are expected, particularly in the process of tanning. Practically the only method that has been used for many decades for converting kid, lamb, and sheep skins into gloving leather is that known technically as "tawing," which consists of treating skins with alum, salt, egg-yolk, flour, and a vegetable oil. These substances change skins into extremely supple and "stretchy" leather, but when this is made into gloves it is far from ideal in wear, because it fails to keep the hands warm in cold, wet weather, it is easily soiled and cannot be cleaned without great expense, and it is not very strong in texture. Combination tannages have lately been produced, however, which remove the defects of alumed leather. By means of a light chrome tannage after tawing, the leather is strengthened and made more resistant to water, and can be cleaned with a damp rag or sponge. By tanning skins with the formaldehyde process, or with Neradol, the artificial tannin, for making into suÈde leather, the finished article is not only washable but also resists the action of alkalies and soap. The adaptation of combined tannages in the manufacture of gloving leathers has only lately been developed, and further improvements will doubtless be effected before long.

Lamb, kid, goat, and sheep skins constitute the raw material for gloving leathers, although deer and antelope skins are also used to a small extent. Real kid skins are the best wearing dress gloves, but the great majority of so-called "kid" gloves are made of lamb skins. The raw kid and lamb skins are chiefly of European, Arabian, and Indian origin. Sheep skins from the Cape provide the raw material for a large number of men's gloves, and leather of very good quality can be produced from the best grades. Most of the skins are preserved by drying, or by salting and drying, although some kid skins are wet-salted and packed in barrels for export. It would save leather-dressers a great deal of trouble if they could always get wet-salted skins; but the object of drying them is to reduce the weight and lower the cost of freight. Soaking is done by methods already described (p. 65). Loose flesh and pieces of fat are cut off in order to facilitate the action of the depilitant, of which the best for glove leather is undoubtedly a paste of lime and red arsenic. Seven or eight parts of lime to one of arsenic is a satisfactory proportion, the quantities to be mixed depending on the number of skins to be treated, as a fresh mixture should be made for each lot, or "pack" as the tanner terms it. The lime should be well broken up, or, better still, pure powdered lime should be used and the red arsenic well mixed with it; a little water is then added to slake the lime gradually, and the mixture is stirred to promote chemical reaction. The compound is further diluted with water until it has the right consistency and the colour has changed. The reaction generates great heat, and the "paint" should, therefore, not be used at once. The flesh side is mopped with the paint and the skins are folded flesh to flesh. After a few hours, or as soon as the hair or wool is loosened, the skins are dehaired or dewoolled. The hair or wool is not allowed to come into contact with the depilitant, otherwise it would be damaged. In large yards, the white hair is separated from the coloured, as it is worth nearly twice as much. Wool is sorted into different qualities, of which the number may vary from four to eight, or even nine, according to the class of skins treated. The pelts are then thoroughly washed and placed in lime liquors, where they remain for one or two weeks, being hauled and set in the usual manner. Fleshing and piecing or trimming are the next operations, and then follows the very important process of puering, which, in the case of glove leather, must be thoroughly done so as to reduce the pelts to a very soft and flaccid condition. Success in the making of glove leather depends largely on the "puering" process.

In most of the English tanneries a decoction of dog manure is used, at a temperature not exceeding 90° F., but on the Continent the artificial puer, oropon, is preferred. It is much safer to use and more uniform in its action than excrement, which develops bacteria rapidly in contact with gelatinous pelts, and could ultimately destroy them entirely. After puering them, the pelts are well washed and submitted to the process of drenching, which consists in putting the skins into a warm infusion of bran or pea-flour and leaving them covered until the following morning. The slightly acid fermentation causes the pelts to rise to the top of the vat. They are pushed into the liquor again with a pole and stirred round. This is repeated three or four times to prevent damage to the grain. The process is often done in the paddle-vat (Fig. 25), in which the bran liquor is circulated for several hours before the pelts are allowed to remain quiescent. Drenching thoroughly purges the pelts of the last traces of lime, and puts them in suitable condition for being made into leather. The pelts are then rinsed in tepid water and "scudded" on the grain with a slate or vulcanite tool, shaped somewhat like a dehairing knife. The scud removed consists of dirt, dissolved lime salts, short hairs, and pigment. Machines are rapidly replacing manual labour for this operation.

The alum tannage, known technically as "tawing," is largely used for kid and lamb gloves. The tawing mixture is composed of alum, salt, egg-yolk, and wheaten flour. The proportions used vary considerably in different tanneries, but the following is a typical recipe: 4 lb. alum, 2 lb. salt, 1 lb. salted egg-yolk, or the yolks of twenty fresh eggs, and 5 lb. flour for 100 lb. of pelts. The flour is made into a paste, the egg yolk is diluted in warm water and mixed with the flour, the salt and alum are dissolved and added, and the mixture thoroughly stirred. A suitable quantity of water (about 2 gals. per 100 lb. pelts) is then placed in the drum tumbler, the tawing mixture is added, and the drum revolved for a few minutes before putting the pelts in. The process is completed in two or three hours in the case of thin skins. It is a good plan, however, to leave them at rest in the drum for a day, after which they are piled up overnight to allow further combination of the tawing materials with the fibres of the pelts. The leather is then dried out completely, damped in clean sawdust, or by sprinkling with water, levelled by shaving if necessary, staked over an upright knife fixed in a wooden stand or by machine, and dried in a hot stove. In this condition, or in the "crust," as dressers term it, the leather is allowed to remain several weeks to "age," a most essential process for the production of soft, and supple glove leather.

Dressing and dyeing are begun as soon as the leather is satisfactorily aged. The skins are uniformly soaked in warm water, dyed, and re-dressed with egg yolk ("re-egged"), to which a small quantity of olive oil, or a sulphonated oil, is added. Some dressers prefer to give the second tawing mixture before dyeing, but the advantage of dressing the leather after dyeing is that the colour is securely fixed. In "re-egging," many dressers use a similar mixture to the first dressing. The dyeing process is of great importance, since the colour must be fast. The leather is dyed either in the drum or on a convex table. In the former case, the leather is naturally coloured both sides, while, in the latter, it is stained with a brush on the grain side only. Staining is the more difficult method. Kid glove leather may be dyed with aniline colours, or, as more generally practised, with natural dye-woods as a base and aniline dye for top-colouring. The great advantages of the latter method are economy in dye-stuffs and increased depth of colour. The skins are first prepared for dyeing by brushing with, or drumming them in, an alkaline solution. Stale urine was largely used for this process, but ammonical salts are now generally preferred, if only for sanitary reasons. The skins are then drummed or paddled in, or brushed with, dye-wood liquids which have been carefully strained. A large selection is available, including fustic, cuba wood, saffron, peachwood, logwood, sappan wood, cutch, Persian berries, gambier or terra japonica, and golden tan bark.

Light and medium brown can be obtained from these dye-woods without the aid of aniline colours; but for dark shades, and to increase the brilliancy of other colours, a top dye or coal-tar dye is often given.

The natural dyes are further developed with "strikers," which mainly consist of metallic salts. Iron, copper, and zinc sulphates, nitrate and acetate of iron, bichromate of potash, and titanium salts (titanium lactate, titanium potassium oxalate, and tanno-titanium oxalate) are the most important. The lactate, sold commercially under the name of "corichrome," is especially suitable, as, unlike the mineral acid salts, especially the sulphates, it has no destructive effect on the fibres of the leather.

Dye-woods are now concentrated in the form of a paste, or dry extract, the latter being the more reliable. They are also very convenient to use and dissolve, while mixtures are, of course, easily prepared. A good tan shade on Cape sheep can be obtained by mordanting the leather with a solution of 1 lb. of bichromate of potash for every 100 lb. of leather, drumming it in 8-9 lb. of pure gambier, and then with a mixture of cuba wood extract, 1 lb.; fustic extract, 3/4 lb.; Brazil wood extract, 1/2 lb.; and logwood extract, 1/2 oz. After drumming the leather in this dye liquor for about an hour, the colour is developed with corichrome. If a darker shade be required, the leather can be treated with a suitable basic dye. After dyeing the leather, some dressers only fat-liquor it with egg-yolk and a small quantity of olive oil, while others prefer to re-dress it with a similar mixture to that used for tawing, namely, alum, salt, egg-yolk, and flour; but, where titanium salts are used, the latter method is not essential, because titanium has tanning properties. When dry, the leather is ready for finishing, but it is advisable to keep it in store for a few days before packing it in damp sawdust or sprinkling it with water to prepare it for the operation of staking. Anything more unlike leather would be difficult to imagine at this stage, but, after stretching the skin in the staking machine, or by drawing it over the upright stake, the dry, stiff, and shrivelled leather is reduced to a very supple condition. The flesh side of the leather is then pared with the moon-knife, or in the shaving machine, to equalise the thickness. In some works, a special tool which pares the leather on a flat table is preferred; this particular operation is called "doling." The flesh side is finished by fluffing it on the emery or carborundum wheel (Fig. 33). Finally, the grain is brushed and polished with the glass sleeker, or ironed.

Chamois leather has been largely used for gloves of late years, but this leather has the defect, in common with suÈde leathers, of getting soiled much more quickly than grain leathers, such as kid, lamb, or Cape sheep. Nevertheless, suÈde and chamois gloves are likely to remain fashionable to a more or less extent. The manufacture of chamois leather is described on page 144. Sun-bleached skins are the best for dyeing, especially if delicate shades are wanted. The frontispiece shows a field covered with skins bleaching in the sun. Chemically bleached leather is likely to become discoloured after dyeing. Defective skins are often dyed with pigments (dust colours), and this system is also applied to skins which have to be dyed such delicate shades as cannot be produced by wood or aniline colours. Although it gives attractive results to the eye, and certainly covers up any defects of the grain, this method of dyeing is not altogether satisfactory, as the leather remains unpleasantly dusty in wear for quite a long time.

The dyeing of chamois with wood-dyes or coal-tar colours is by no means easy, but this method gives the best results when successful. The grease must first be removed from the leather with a solution of 5 lb. of borax or 3-1/2 lb. of soda for every 100 lb. of leather. If the leather is still greasy on the surface, a further quantity of soda or borax is given, after which the leather is well washed in warm water, sumached, rinsed to remove the particles of sumach, and mordanted with titanium salts. The dyeing is then done with anilines or wood-dyes, or a combination of both, and this is followed by fat-liquoring with egg-yolk and a sulphonated oil. The finishing operations are staking and fluffing.

To get a good, fast black on chamois and suÈde leathers is one of the difficult processes in the leather trade, although it is easier to get a good black on alumed or chromed leather than on vegetable-tanned. Alumed leather is washed in a solution of borax or carbonate of ammonia to remove uncombined dressing in order to prepare it for dyeing. Chrome-tanned suÈde leather does not need this preparation. The leather is first mordanted with dye-wood extract, of which a suitable mixture is logwood and fustic, or logwood and quercitron, in the proportion of 4 lb. and 2 lb. to every 100 lb. of leather. After drumming the leather in this solution for about an hour, a weak solution of copperas (ferrous sulphate) and bluestone (copper sulphate) is added, and the milling is continued for twenty minutes, when the leather is well prepared to receive the black dye. Instead of the iron and copper salts, corichrome is often preferred, as it is quite safe to use, whereas iron salts have a destructive action on the fibres of the leather, unless the precaution be taken to mordant the skins with a good quantity of dye-wood extract. Following the application of the iron or corichrome striker, the leather is dyed with suitable aniline black (leather black, or corvoline) and finally fat-liquored to nourish the leather, and to fix and intensify the black. This recipe also gives good results where the skins are dyed only on the flesh side, the solutions being applied with a brush.

White Washable Leather

Among the new kinds of leather for gloves, none is more remarkable or more useful than the washable sheep or goat skins. The great advantage of this leather is that it can be washed in warm water and soap any number of times without injury, whereas gloves of ordinary tawed kid and lamb skins have to be dry cleaned and cannot be renovated many times. An additional advantage of washable leather is its warmth. After being dehaired, puered and drenched, the skins are drummed in a solution of formaldehyde and soda. In two or three hours, the skins are tanned, and are then treated with a solution of sulphate of ammonia. The quantities required are about 3 lb. of formaldehyde (40 per cent.) and 8 lb. of sodium carbonate (80 per cent.), and 1 lb. of sulphate for 100 lb. of pelts, using sufficient water to cover the skins well in the drum. This tannage produces a white but somewhat thin and empty leather, and the fat-liquoring must, therefore, be filling and softening. An emulsion of white curd soap and olive oil, or of egg-yolk and neatsfoot oil, is suitable. "Crestanol," a special preparation, also gives satisfactory results, since it is adapted for giving nourishment and resiliency to thin, empty leather.

Fancy Leathers

The best known of the fancy leathers is "morocco." This variety has been made for ages, and the name probably originated from the fact that very fine leathers of this kind were manufactured in Morocco a few centuries ago. History records that a similar leather, dyed red, was made in the ninth century before the Christian era.

The best morocco leather is made from Continental goat skins, which are mostly obtained from Central Europe and Spain. The Norwegian goat skins are also said to be of good quality for the morocco finish. An inferior morocco leather, which is produced in large quantities, is manufactured from East India goat skins, while a cheaper grade still can be produced from certain classes of East India sheep skins. The real moroccos are tanned in sumach, but the cheaper sorts are tanned in India with babool or turwar bark and re-tanned in sumach in the countries to which they are exported, chiefly Great Britain, Germany, France, and America. One of the best methods of sumach-tanning goat and calf skins is that known as the "bottle" tannage. Each skin is doubled over and sewn by machine round the edge, leaving part of the neck unsewn. The skins are then turned inside out and filled with a strong infusion of sumach, and floated in a tub containing sumach liquor. After being a few hours in the tub, the skins are heaped one above the other in a large pile, where the pressure forces the tannin through the skins. The process can be completed in twenty to twenty-four hours, after which the skins are cut open, rinsed, and finished in the usual manner. This method of tanning is now largely replaced by the use of paddle-vats (Fig. 25).

The dyeing and finishing are somewhat similar to that of coloured boot upper leather, except that the leather is slightly oiled on the grain instead of being fat-liquored. There are several different methods of graining morocco leather; some of the grains are made naturally by pressing the leather, when folded over, with a cork-covered board, while others are first embossed in various ways and then boarded. The well-known "crushed morocco" is produced by glazing the grained leather under heavy pressure.

Skivers, the grain splits of sheep skins (see p. 145) are extensively used for fancy articles. The majority are finished with a smooth grain for hat-bands, bookbinding, and linings. The grain of a sheep skin is, naturally, soft, and not very strong. To stiffen and strengthen the grain, an artificial layer, consisting of paste finishes, is often applied. Skins finished in this manner are termed "paste grain skivers." These are largely used for bookbinding and cheap purses. Sheep grains are sometimes given a finish somewhat similar to that of leather bags. This is produced in a printing machine by means of a copper roller which is run over the damp (but not too wet) leather. The skins are then described as "long-grain" skivers. The grain surface of sheep skins is particularly suitable for embossing, and wonderful imitations of all kinds of skins can be reproduced on skivers.

The fancy leather trade is not confined to these imitations, however, as real lizard, seal, ichneumon, alligators, crocodile, shark, porpoise, snake, and even frog skins (Japanese) are utilised.