Page:Encyclopædia Britannica, Ninth Edition, v. 14.djvu/407

 LEATHER 389 liquor, and in no case are they sewed into bags, as is most commonly the case with entire sheep and goat skins. The splitting machine used for split sheep skins has two rollers, the lower one of gun-metal and solid, and the upper made of gun-metal rings, while between the two rollers, and nearly in contact, is the edge of the sharp knife, to which an oscillat ing movement is given by a crank. When a skin is intro duced between the two rollers, it is dragged through against the knife edge and divided, the solid lower roller support ing the membrane, while the upper one, being capable of moving through a small space by means of its rings, adjusts itself to inequalities in the membrane ; where this is thin the rings become depressed, and where it is thick they rise up, so that no part escapes the action of the knife. Skivers are finished white, or in colours in variously lined or diced patterns, and in imitation grain, and are principally em ployed for hat and other linings and various purposes in which they meet little strain or tear and wear. Danish Leather is tanned sheep and lamb skins princi pally, but goat and kid skins also are used. The tanning medium is willow bark, and the leather, bright in colour and highly elastic, is used for strong gloves. The same name is also applied to tawed lamb skins, dressed and finished on the flesh side. Alligator Leather. For a number of years leather tanned from the skins of the Mississippi alligator has formed an item in the trade lists of the United States, and it is now also being sought after in tha European markets. The industry was started about the year 1860, and centred first at New Orleans, the raw skins being obtained from the rivers of Louisiana. Now, however, the skins are princi pally procured in Florida, and the tanning is a considerable industry in Jacksonville. The parts of the skin useful for leather making are the belly and flanks, and these portions alone are steeped in lime to preserve them for the tanner. Alligator leather, which has a scaly surface, is useful for fancy boot and shoe making, and for many small articles such as cigar cases, pocket books, &amp;lt;fec. Kangaroo Leather. The Australian colonists have turned their attention to the preparation of leather from the skins of the kangaroo, wallaby, and other marsupials native to their continent. These skins are both tanned and tawed, the principal tanning agent being the mimosa bark, which abounds in Australia. The leathers they yield are of excellent quality, strong, and elastic, and rival in texture and appearance the kid of European tanners. The cir cumstance that the animals exist only in the wild state renders this a limited and insecure source of leather. Tawed Leather. Under the term tawing is embraced the preparation of leather by the action of mineral substances on hides and skins. In the pro cess of tawing the substance principally employed is alum or some of the simple aluminous salts, although many other inorganic salts have been proposed, some of which have given considerable pro mise of practical success. The system of tawing is principally ap plied to thin and light skins of sheep, lambs, kids, and goats, although in former times much heavy leather was tawed for military belts, heavy gloves, machine belts, &c., for most of which purposes, however, sumach-tanned or similar leathers are now found more applicable and durable. The products obtained by tawing are of a pure white colour, whence the name white leather is frequently applied to goods of this class. The most important departments of the tawing industry are the calf kid manufactures for boots and shoes, and glove kid or glace leather tawing, the products of which are exclusively devoted to glove making. A large number of white tawed sheep skins are also used by druggists and perfumers as tie- over leather for bottles, and for linings by bootmakers, &c. Calf Kid. The various steps of preparation through which the light skins suitable for this manufacture pass, in respect of softening, liming, nnhairing, puring, and drenching, are similar to the process by which morocco skins are prepared for tanning. The tawing itself is accomplished in a drum or cylinder the same as the currier s stuffing wheel, into which is introduced for one hundred average skins a mixture consisting of 20 lb of alnm, 9 lb salt, 40 Ib flour, 250 eggs (or about 1 gallons of egg yolk), | pint of olive oil, and 12 to 16 gallons of water. In this mixture, at a temperature of not more than 100 Fahr., the skins are worked for about forty minutes, by which action the tawing is completed. After the withdrawal from the drum the skins are allowed to drain, dried rapidly by artificial heat, damped, staked out by drawing them over a blunt steel tool, and then wetted and shaved down on the beam to the required thickness. Next they receive, if necessary, a second treatment with the tawing mixture. The dyeing or colouring follows, which in the case of calf kid is always black, the colour consisting of a compound of bichromate of potash, stale urine, logwood extract, and copperas. It is applied either by brushes on a table, or by dyeing the leather in small vats as in the parallel case of morocco leather. The dyed leather is washed with pure water, dried, grounded with a curious moon knife, stretched in all directions, ironed, and oiled on the flesh siJe with a mixture of oil, wax, &c. Glove Kid. In the preparation of kid leather for gloves the tender skins of young kids alone are used for the best qualities, but for a large proportion of such leather young lamb skins are also tawed. The genuine kid leather is for the most part produced in France, specially at Annonay and Paris, while lamb kid is more particularly a product of Germany, Austria, and Denmark. In all stages of the preparation of this leather the utmost care and attention are requisite, and it is specially of consequence that the operations preparatory to tawing should receive thorough attention. The unhairing is best effected by steeping the skins in a mixture of lime and orpiment, and, while the general sequence of unhairing, fleshing, bating with dog s dung, scudding, washing, and treating with the bran drench is the same as in the case of other skins, much more attention is bestowed on each stage in order to maintain the smoothness of grain, and to obtain a thoroughly clean elastic pelt, than is absolutely needful for any other variety of leather. The tawing mixture consists for each 100 lb of skins of about 28 Ib of flour, 3^ lb of alum, nearly 1 lb of common salt, and 230 eggs. These substances are made into the consistency of a cream with water, and placed either in a vat or in a revolving drum. In the former case, the skins are trodden with the feet, while in the latter they are tumbled about. The tawed skins are hung over poles, grain side inwards, and dried rapidly ; when hard dry they are heaped in a damp place to soften a little, then damped by passing them through water, next trodden out by foot on a ridged or barred floor, staked or stretched over a blunt knife, partly dried, and again staked and dried thoroughly. For dyeing, the skins are first washed out in warm water to free them from superfluous alum, and then again &quot; fed &quot; with yolk of eggs and salt. For bright colours such as soft greys, lavenders, and yellows, the skins are plunged into small dye vats of the proper dye colours ; but for all the dai ker colours the skins are stretched out on a table and the dye stuffs applied with a brush. In the latter case the leather is first grounded with some alkaline solution, then dyed mostly with logwood, brazil wood, fustic, Prussian berries, or preparations of indigo, aniline colours being now little used for glove dyeing. The dye is mor danted by a wash of the sulphate of either zinc, copper, or iron, which operation also clears and develops the colour. After dyeing it only remains to free the leather from superfluous moisture, dry it, and then with slight damping stake or stretch it out once or twice, which finishes the preparation of this valuable class of leather. The &quot;feeding&quot; of kid leathers with yolk and sometimes oil pro- ducesapartial shamoying, softening the texture andgiving the leather that peculiar suppleness to which much of its value is due. The flour added, by means of the gluten it contains, is supposed to facilitate the absorption of the alumina and thus hasten the tawing. Hungarian Leather consists of hides and heavy skins partly tawed and partly shamoyed. In the, preparation of this leather it was formerly the practice to shave off the hair with a sharp knife, but now the hides are unhaired either by sweating or liming. After tawing with alum and salt the leather is stuffed by first heating it over a charcoal fire and impregnating the hot leather with tallow, or, as is now common, by working it in a drum with a hot mixture of cod oil and tallow. This leather, being comparatively cheap, is much used on the Continent for common saddlery purposes, for which it is blackened, and it is also serviceable for machinery belts. A leather has been patented by Professor Knapp, in which the active tanning or tawing principle is a basic salt of the cxide of iron. It was intended principally for sole leather, but it does not appear to have met with practical success, and its manufacture is under stood to have been abandoned. Heinzerlinrj s Chrome-tanned Leather. Quite recently a large amount of attention has been devoted to a system of tanning or tawing by means of chromium compounds patented by Dr Heinzerling, a German chemist. The oxidizing power of chromate salts, and the deoxidizing effect which organic matter has upon these salts, have long been recognized, and the knowledge of this action and counter-action has led to many unsuccessful attempts, in the past, to use chromates in tanning. It is claimed, however, that the difficulties have been overcome by Dr Heinzerling s process, which consists practically in the use of bichromate of potash, chloride of