Very fat skins, such as dogs' skins, may, if perfectly fresh, be nailed out and gone over with a saturated solution of borax, or a solution of one part borax to one-eighth part saltpetre, and left to dry in the shade for three months, after which they may be scraped, and their natural fat will, after all superfluity has been removed with plaster, etc.., be found to have sufficiently imbued the under or proper skin to render the final greasing unnecessary.
The two foregoing processes seem to have been modified with some success by Mr. R. Backhouse, of Stockton-on-Tees, whose process is spoken of in the Field of June 3rd, 1882, as follows:
"The skin, which should be removed from the animal as soon as possible after it has been killed, is stretched and tacked on to a board, the flesh side being outwards. This is at once covered with lard carefully spread over the entire surface, no portion being allowed to escape. As the moisture dries out of the skin, the lard enters the pores and supplies its place, and in about a week's time (the lard being carefully renewed when requisite) the skin will have altered its character, in consequence of being penetrated by the grease. It is then removed and washed thoroughly in warm water and soap until the external grease is removed.
During the drying it is necessary to pull and stretch the skin in all directions, so that its texture opens, and it becomes white, owing to the admission of air into the pores; this stretching is accompanied, or rather preceded, by careful scraping or currying with a sharp knife or razor, to remove the fleshy matters and render the skin thinner. With the larger number of skins the process is successful; but some few go bad, apparently from not absorbing the lard with sufficient rapidity."..
Possibly the species of mammals treated may have something to do with this, the skins of carnivorous animals bearing exposure better than those of the rodentia — hares, rabbits, squirrels, etc.., and insectivora — bats, shrew-mice, and moles — indeed, the latter animals must be skinned almost as soon as they are dead, or the skin turns "green" and goes bad in a very short time. No doubt the vegetable and insect food consumed by these cause fermentation after death, with the resultant putrefaction of the bowels and the thin coverings of the latter.
I would here point out, however, that small skins — cats', rabbits', etc.. — will be perfectly preserved if stretched out whilst fresh, cured with the chloride of lime preservative (No. 4), and then finally treated with lard and essence of musk, and finished off by either of the preceding methods to render them clean and supple. A correspondent who had treated some cats' skins by this method writes to say he has "succeeded in curing some cats' skins in an admirable manner" by following these instructions.
A very convenient mixture of borax and another natural salt has been brought out by Mr. Robottom, of Birmingham (see Chapter I). I have given his preparation a long and patient investigation, and can recommend it for small skins, while its convenient form, cleanliness, and low price, place it within the reach of all amateurs.
Equal parts of salt, alum, and Glauber's salts, mixed with half a part of saltpetre, the whole rubbed in several times a day, has been recommended, but I have not tried it.
A mixture of sulphur and arsenic with soft soap is sometimes used to dress skins with, and if left on for about a year certainly renders them very pliant, after the removal of the grease.
The North American Indians, I believe, smoke their deer skins, etc.., and after working them, use brains to dress them with.