As the tanning advances, the liquor should be renewed seasonably, and its strength increased in a ratio proportionate to each stage of tanning.
The question, “Is the leather to be tanned so as to barely pass in market, or to be well prepared, so as to make firm and solid leather?” involves a consideration of much importance.
Every one interested in the science of tanning should purchase and study the able and elaborate work upon the subject by Morfit. No portion of this important art is left untouched, and the work gives abundant evidence of laborious research, and intelligent compilation, combined with a thorough knowledge of the subject.
CHAPTER IV.
HIBBARD’S PROCESS OF TANNING.
We herewith give the specification of this important patent, allusion to which is made in the letter of Dr. Reid:
To all whom it may concern:—Be it known that I, William W. Reid, of the city of Rochester, in the county of Monroe, and State of New York, assignee of Letters Patent of the United States, granted to Herman Hibbard, of the town of Henrietta, in the county and State aforesaid, for certain improvements in “Tanning by Tannin and acids,” which Letters Patent, bearing date the 16th day of October, 1849, were assigned to me on the 23d day of October, of the same year, by deed, which deed was duly recorded on the 24th of Nov., year aforesaid, believing that said Letters Patent are inoperative, and invalid by reason of a defective specification, have surrendered the same, and according to the requirements of the Acts of Congress in such case made and provided, have applied for a re-issue of Letters Patent, for the same improvements under the specification of the words following, viz.: The invention and discovery of Herman Hibbard, consist in new and useful improvements in the preparing of hides and skins for tanning, and in the art or mode of tanning the same, with or without the hair or wool upon them, thereby making leather suitable for the various purposes to which hides and skins thus tanned may be applied.
First, the nature of his invention, so far as relates to the preparation of hides and skins for tanning, consists in the use of a composition of lime, wood-ashes or potash and salt, for the purpose of removing hair or wool, and also for the process of “Liming,” so called, instead of using lime alone as in the old method.
Lime and ashes or potash, and even salt in weak solution, have been used separately for the purpose of removing hair and wool, and also for the process of “Liming,” that is for removing grease, mucus, and other impurities from hides and skins, but not as above combined.
It requires several days and sometimes weeks to effect these several objects, by the use of lime alone. Moreover, lime being nearly insoluble, the hides become impregnated therewith, so that bates and drenches and much labor are required to remove it, before the hides are in a suitable condition to receive the tannin, in consequence of which, their muscular fibre and texture are materially injured. But potash being very soluble, is easily washed or worked out by water alone; besides, it has a greater affinity for fat or oil, and makes a soluble soap, which is also easily worked out; but lime makes an insoluble soap, which is removed with more difficulty; potash being soluble, penetrates and softens the hide more speedily, and thus enables the lime itself to act sooner than it could alone. But fresh quick lime loosens hair sooner than potash. Thus the two conjoined, subserve a better purpose than either singly.
Salt, in solution, also aids in softening dry or hard hides. It protects the substance of the hide from the too caustic action of the alkalies—loosens dirt, grease, &c., and thereby purifies the skin. It might be omitted in treating salted hides unless soaked too long in water. But in all cases it preserves the substance and weight of the hides, while undergoing the liming process.