HIDES USED FOR SOLE-LEATHER.—The principal sources of hides for sole-leather are :— (I.) Market hides, from the cattle slaughtered for food in the United Kingdom. These are received by the tanner, fresh or slightly salted, and are either bought directly from the butcher, or, now more commonly, through the auction markets established in all large towns. The latter system, while it perhaps slightly enhances the price of the hides to the tanner, ensures him a better classi fication according to weight, and, in some cases, as notably in that of Glasgow, a better flaying, through an organized system of inspection and sorting. The Scotch hides, being mostly from Highland cattle, are many of them small and very plump, for, as a rule, the bides are thickest on those animals which are exposed to cold and the hardships of out-door life. On the other hand, the hides of highly-bred cattle are apt to be thin and spreading; and, if they have been kept much indoors, and negligently managed, the grain of the hide is injured by the dung which adheres to it. The Irish hides are usually somewhat roughly flayed.
(II.) South American bides are from the River Plate, Uruguay, and Rio Grande. Those from the River Plate are considered the best, as being stoutest and finest in texture. They are usually cured by salting, and are known as "saladeros," "estancias," and "mataderos," according to the slaughter and cure. The saladeros are the best, and are from cattle killed at large slaughtering establishments on the coast. The estancias are from cattle killed in the interior, and are worse in flaying than the saladeros, but free from the objectionable dark cure of the mataderos, which are killed by the city butchers. Many hides are brought from Brazil, and are generally both salted and sun-dried, or simply stretched out and dried. Hides are also imported from Valparaiso, both dry and wet-salted.
China and W. Indies hides are mostly dried. French market htdes have been of recent years largely imported ; they are mostly well-flayed, and some of them very heavy, but are sold at original butchers' weight, and; in the experience of some tanners, the result in leather is 5-6 per cent. lees than from English market hides. They usually lose about 25 per cent. in sculling and salting. Lisbon hides are often well flayed, but are frequently branded, and the grain is injured by insects. They yield considerably more leather than market hides in proportion to weight. Hambro bides are salted, but mostly wet and ill-flayed.
Preparation of Hides for Tanning.—Market hides merely require a slight soaking in fresh water, to remove blood and dirt, before unhairing. Salted hides should be soaked somewhat longer, and in soveral changes of water, so as to remove the salt before limeing. Dried hides, however, require more lengthened treatment. Before they are prepared for tanning, they must be brought back as far as possible to the condition of fresh hides, and, for this purpose, must be thoroughly soaked and softened in water. There aro many ways of doing this: sometimes hides are suspended in running
water ; sometimes laid in soaks, which may be either renewed, or allowed to putrefy ; sometimes in water to which salt or carbolio acid has been added, to prevent putrefaction.
The first of these methods, were it desirable, is rarely possible in these days of River Pollution Acts ; of the others, it is difficult to say which is better, since the treatment desirable varies with the hardness of the hide and the temperature at which it has been dried. The great object is to thoroughly soften the hide, without allowing putrefaction to injure it. As dried hides are often damaged already from this cause, either before drying, or from becoming moist and heated on ship board, it is frequently no easy matter to accomplish this. The fresh hide, as has been seen, con tains considerable portions of albumen, and if the hide is dried at a high temperature, this becomes wholly or partially coagulated and insoluble. The gelatinous fibre and the coriin (if indeed the latter exists ready formed in the fresh hide) do not coagulate by heat, but also become less readily soluble. Eitner experimented with pieces of green calf-skin of equal thickness, which were dried at different temperatures, with results given in the following table :— Hence it is evident that, for hides dried at low temperatures, short soaking in fresh and cold water is sufficient, and, except in warm weather, there would be little danger of putrefaction. With harder drying, longer time is required, and it may be necessary to use brine instead of water. A well-known tanner recommends a solution of 30°-35° barkometer (sp. gr. or about 5 per cent. of Neel). This will have a double action, not only preserving from putrefaction, but dis solving a portion of the bide-substance in the form of conic. Although this is undoubtedly a loss to the tanner, it is questionable if there is any process which will soften overdried hides without loss of weight : even prolonged soaking in cold water at too low a temperature to allow of putre faction will dissolve a serious amount of bide-substance. Water containing a small quantity of carbolic acid has been recommended for the purpose, and will' prevent putrefaction, while it has no solvent power on the hide, but, on the contrary, will coagulate and render insoluble albu minous matters. Borax has been proposed for the same purpose, and, in strong solution, certainly prevents putrefaction, but is probably too costly. Sulphide of sodium and other sulphides seem to have considerable effect in softening dried bides, from their property of attacking bard albuminous matters, without injuring the true hide-fibre. A little sulphide of sodium is sometimes added to obstinate hides in the stocks.