Second, the nature of Hibbard’s invention, so far as it relates to the process of tanning, consists in the use of a composition of salt, sulphuric acid, and sumac, oak, hemlock bark, or any other tannin used for tanning.
The salt, sulphuric acid, and tannin being mixed together in water, in certain proportions hereafter mentioned, a portion of the salt is decomposed by the sulphuric acid, forming sulphate of soda and setting the muriatic acid free, which (the muriatic acid) being absorbed by the water acts directly and rapidly on whatever of the alkalies may yet remain in the skins, dissolving and removing them, while it acts with equal rapidity on the hide itself, “raising it,” or opening its pores, prepares it to receive the tannin, which, being present also in the mixture, immediately unites with the gelatine of the hide, forming leather more expeditiously than by the old method.
To enable others skilled in the art of tanning to use this method, let them observe the following:
For unhairing and liming, so called, and for pulling wool, prepare and use the following composition, which we denominate—
Composition No. 1.—Good wood ashes, 1 bushel (or potash about 5 pounds); fresh slaked lime 4 quarts; salt about 3 quarts; water about 100 gallons.
These ingredients may be mixed together and the hides be put into the mixture, for unhairing and liming. But for pulling wool, take lime and ashes equal parts, and salt 1 quart, to one bushel of the mixture and mix with water sufficient to make a thin paste, which is to be applied to the flesh sides of the skins in the usual way, and kept at a temperature of 60° to 68° F.
Or a better method may be to leach the ashes, or, when potash is used, to dissolve it in the water. To the clear ley add the lime and salt, and use the mixture for unhairing and liming. But for pulling wool mix 1 bushel of lime and 1 quart of salt with good strong ley, making a thin paste, which apply to the flesh sides of the skins, as already described.
A little practice will enable the operator to judge of the proper strength of composition No. 1. It should have a slippery feel and quite a sharp alkaline taste. It is readily made stronger by the addition of more materials, or weaker by adding water.
The above quantities and proportions serve as a general guide. The lime and ashes or potash may be used in various proportions, but it is desirable that as little lime as possible to produce the desired effect, should be used, because of its insolubility and of its insinuating itself into the substance of the hide. The hides or skins having been properly soaked, softened, and broken, are to be put into composition No. 1, in a vat or vats, and handled in the usual way. The temperature may be kept at 50° to 60° F.
As soon as the hair will come freely, they must be taken out and put into clean soft warm water, and soaked several hours, then thoroughly worked, flesh and grain, on the beam. Then put back into the water, soaked again and worked again, till they are sufficiently reduced. They are then ready for the tanning process. As a general thing, bates and drenches will not be required, because the potash being soluble, and the little lime used, are easily washed out with water, and because composition No. 2, about to be described, used in the tanning, accomplishes the identical objects to be obtained by bating and drenching. If any prefer, they may prepare their hides and skins after the old method. They can be tanned just as well by composition No. 2, but skins and hides prepared by the foregoing method will make heavier and stronger leather, than when prepared by the old process of tanning and bating.