[CHAPTER VII.]
SOLE-LEATHER:—Preparing the Hides.
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 classification according to weight, and, in some cases, as notably in that of Glasgow, a better flaying, through an organised 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 hides 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 hides 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.
Chinese and West Indian hides are mostly dried. Chinese hides are occasionally infected with Bacillus anthracis, which produces the dangerous "malignant-pustule," or "wool-sorters' disease." Hence any pimple appearing after working with such hides should have immediate medical attention. French market hides 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. less than from English market hides. They usually lose about 25 per cent. in skulling 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' hides are salted, but mostly wet and ill-flayed. Very heavy hides are produced in the Rhine district and in Switzerland.
For further information about hides, see the Commercial Section.
Preparation for Tanning.—Market hides should be well washed in fresh water, to remove blood and dirt, before unhairing; but prolonged soaking dissolves a portion of hide-substance, and probably reduces weight, though it facilitates the action of the lime. It is very advantageous if grease and flesh, and also dung can be removed before liming, and if hand-labour is too costly machinery might be employed. Salted hides should be soaked somewhat longer, and in clean water, so as to remove the salt before liming. This water should be frequently changed, since 10 per cent. brine dissolves coriin freely (see [p. 19]). Dried hides 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 are 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, borax, or carbolic 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, contains 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. Gelatin dried at 266° F. (130° C.) can only be redissolved by acids, or water at 248° F. (120° C.). Eitner experimented with pieces of green calf-skin of equal thickness, which were dried at different temperatures, with results given in the following table:—
| Sample. | Temperature of Drying. | Remarks. | Time of Softening in Water. | Remarks. | Coriin Dissolved by Salt Solution. | ||||
| I. | 59° F. (15° C.) | In vacuo | 24 hours |  | Without mechanical work |  | 1·68 per cent. | ||
| II. | 711/2° F. (22° C.) | In sun | 2 days | 1·62 " | |||||
| III. | 95° F. (35° C.) | | In drying-closet | 5 " | twice worked | 0·15 " | |||
| IV. | 140° F. (60° C.) | " |  | Refused to soften sufficiently for tanning |  | Traces. | |||