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.
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.
For tanning, make and use the following which we denominate—
Composition No. 2.—Take sumac, oak bark, quercitron, or any other
tanning material, either singly, or combined; leach and make a strong
infusion or ooze. To every 100 gals. of ooze add salt, 20 lbs.;
sulphuric acid 2 pints.
These quantities serve as a general rule. A little experience will
enable a workman to determine by the color and taste, as to the
requisite proportions and quantities and strength of the composition
without weighing or measuring.
The salt should always be in excess over the acid. If it is considerably
more so, no harm can accrue, but if the acid should be in excess, injury
might be done. There should be sulphuric acid enough to decompose enough
of the salt to liberate an equivalent of muriatic acid, of which there
should be as much as is sufficient to give the hides a uniform color,
and cause them to swell or puff up slightly.
The muriatic acid thus generated by the decomposition of the salt, by
means of the sulphuric acid, attacks the alkalies that may remain in the
hides, dissolves or converts them into soluble muriates of lime or
potash, and thus acts as a bate and drench on the hides, to clean them,
while at the same time it opens their pores, so that they imbibe the
tannin more rapidly. It also precipitates or decomposes a portion of the
coloring matter of the ooze, and thereby renders the color of the
leather lighter, more lively and beautiful.
If there is a deficiency of acid, so as not to neutralize all the
alkalies remaining in the hides, they will be spotted or dark colored.
They will not raise or swell up. In such case, more of the sulphuric
acid must be added for the purpose of decomposing more of the salt
(which is supposed to be in excess) and thus furnish more of the
muriatic acid.
N. B.—Muriatic acid of commerce may be added to the tannin and salt, and
they will produce nearly the same result; the sulphate of soda would be
wanting, but this also may be added, and then we should have the same
composition, and precisely the same results; and when economy would
warrant it, this course might be adopted, but at the present cost of
these materials, it is cheaper to use sulphuric acid and salt, and thus
generate both the muriatic acid and sulphate of soda; this method is
also more simple.
The hides and skins having been prepared in Composition No. 1, as
already described, they are then to be put into Composition No. 2,
prepared as above, in suitable vats, and handled often in the usual way.
The strength of the composition must be kept up by additions of strong
ooze, and also of salt and acid when necessary, and in such quantities
as will give the original taste, color, &c.
The time required to accomplish the process of tanning will depend on
the quality and size of the hides or skins, or kinds of leather to be
made, and on the strength and temperature of the composition. It the
strength be good, the temperature about 80°, and the handling properly
conducted, most kinds of leather may be tanned in less than half the
time required by the old method of tanning now in use in our country.
When the hides are sufficiently tanned, those designed to be curried may
be curried and finished in the usual way. If the process has been
properly conducted, they will require much less scouring, whereby some
hard labor is saved.
When it is intended to black and finish on the grain, in order to remove
any excess of salt and acid that may remain in them and interfere with
the finishing, after removing them from the vats, soak them an hour or
less in a clear ooze, made of the same kind of tannin used in tanning
them; then rinse and strike them out of clear soft water, after which
immerse them in the following composition:—To every gallon of soft water
add, of good soft soap 1 quart; best sperm or cod oil, 1 pint. Mix and
beat these ingredients well together; after being dipped in this mixture
let them “sammy” or dry partially, then sham set and stuff them. For
stuffing, use common stuffing and soft soap, equal parts, or sad and cod
oil, equal parts; after which, if to be finished on the flesh side,
proceed in the usual way, but if it be blacked on the grain, wet or
sponge them, when nearly dry, on the grain side with a weak solution of
potash or sal soda, then apply a thin coat of blood and acetate of iron,
as used by morocco dressers; let them nearly dry, then repeat the coat
of sal soda and mixture of blood and acetate of iron. Then set them
smooth on both sides, and oil and dry them.
Deer, sheep, and similar skins, designed for buck, or imitation of buck,
such as are used for gloves, mittens, and military trimmings, should be
“frized” after being prepared in Composition No. 1, and unhaired; and
then tanned in Composition No. 2, prepared with sumac. When tanned,
rinse and strike them out of clean soft water, then hang up to dry. When
dry, finish on a perch with a stake, moon-knife, and pumice stone; or,
to make them soft and elastic, they may be milled first, before quite
dry, and then finished with perch, moon-knife, &c., the same as in oil
dressing, but without any oil.
In order to tan hides or skins with fur, hair, or wool on, they must
first be washed thoroughly clean in a weak potash ley, or in soft soap
and water (care being taken not to keep them in so long as to start or
loosen the fur, &c.,) then flesh and break them; rinse in clean soft
water, then tan them in composition No. 2. To make white leather, sumac
should be used in making composition No. 2. What I claim and desire to
secure by Letters Patent, is, first, the process of removing the hair
and wool from hides and skins, and of liming them, so called,
preparatory to tanning by the use of a composition of lime, wood ashes
or potash, and of salt, called Composition No. 1, in the manner above
described.
I also claim the use of a composition of lime and wood ashes or potash,
without the salt, but I do not claim either of these materials
separately by itself.
Second, I claim the process of tanning hides and skins by the use of any
kind of tannin, in combination either with the muriatic acid of
commerce, or with muriatic acid generated by a mixture of sulphuric acid
and salt in water, with the tannin, in the manner substantially as above
described.