TANNING PROCESSES.
More than one hundred tanning processes have been patented in the United
States and Europe, and the cry is, “still they come.” New methods, and
new works upon old methods are constantly presenting themselves. The
London Mechanics’ Magazine states that an important improvement in the
tanning of skins and hides has recently been introduced into that
country by M. Funcke, a practical tanner and currier, of Herdecke,
Westphalia. It consists in counteracting a too rapid action of the
tannic acid upon the surface of the skins. The mode of operation is as
follows:—
The unhaired skins or hides are first passed through a weak liquor of
the soda of commerce, then hung up to dry. They are then steeped in a
common oak, hemlock, or other tanning liquor of the common strength, to
which has been added some vinegar. In this liquor the pores of the skin
are opened, and thus the tannic acid is admitted to the interior. The
next tannic liquor in which the skins are steeped is made a little
stronger with the bark, also some more vinegar, and a little dissolved
sugar is added. The succeeding liquors to which the hides are subjected,
until they are finished, do not differ from those in common use. The
vinegar being a vegetable acid, unites with the alkali of the soda in
the hides, and its carbonic acid is set free in the pores of the skin;
this expands them, and allows the tannin admission to the centre of the
hides in the first tanning liquor. The sugar in the second tannin
liquor, unites with the vinegar, and forms a tannin mixture, it is said,
which is of a softening character, imparting elasticity to the leather.
The strength of the soda ley used to steep the hides in the first stage,
is not above 1°—very weak—and a very small quantity of vinegar is
sufficient for the purpose stated. Any other vegetable acid may be used
in place of the vinegar, but it is the cheapest.
The expanding of the pores of hides and skins by generating a gas in the
tanning liquor by the agency of the carbonate of soda and an acid, such
as sulphuric and muriatic, is not new. It has been tried in this
country, and is known by the name of the “Hibbard process.”
THE PRELLER PROCESS.
This discovery and application is highly approved of in London.
After the hides or skins are unhaired in the usual manner, they undergo
a partial drying, and receive a uniform coating of a peculiar paste
composed of various vegetable and saline substances. The vegetable
substances employed contain a large proportion of starch, such as
barley, rice, or wheat flour, a little gluten, some butter, or oil and
grease, some common salt, and some saltpetre. The hides are laid upon
tables and smeared on the fleshy side, with the said paste, and in that
state are put into the interior of large drums, which receive a rotary
motion, and by which, the hides are greatly agitated, and the paste (by
pegs in the inside of the drums), is forced into the pores of the hides
or skins, or rather they are kneaded along with the paste for two or
three hours, after which they are drawn out. They are then found to be
in a partial dry state, then hung up and aired for two hours, and again
laid upon the table, where they receive another dose of the same paste,
and are again returned to the drums a second time, when the same
operation as that described is again performed. After this they receive
a third smearing with the paste, and are kneaded in the drums, after
which they are taken out and hung up to dry, and are then fit for the
currying process. The leather thus produced is stated to be much lighter
than that produced by oak or other tan barks, but is much stronger and
will wear much better. It is asserted that for machinery bands it is
twice as strong as oak-tanned leather, and that sheep and goat skins are
rendered very tough and durable. It is said that calf skins are tanned
by this process in about three hours, and the thickest ox-hide in three
days.
In noticing this process the “Scientific American” remarked as follows:—
We are not aware that any such process for tanning is described in any
work on the subject, or has been practiced in our country. It is our
opinion that it may make excellent uppers for boots and shoes, but not
so good sole leather as oak bark. It is stated that the brains of
animals is also used in the paste, and that the salt and nitre are only
employed to preserve the animal and greasy matters from putrefaction.
The process has some resemblance to that employed by many tribes of our
Indians for tanning their skins for moccasins and other purposes. They
use the brains of animals, mixed with ley made of the wood ashes of
their fires, and knead the skins and rub them with the pasty mass, upon
the same principle as that employed in the “Preller process.” When the
tanning of the skins is completed according to their notions, they are
finished by drying them, or rather smoking them, in a pit in the ground,
which is covered with bark and some earth. We have seen very good brown
leather made by this process. We are not able to give the exact
proportions of the paste used by Preller, but this does not make much
matter, for some of our tanners can surely make up a paste with flour,
ox brains, and oil or grease, &c., and give it a fair trial, by kneading
a skin or two in a tub, with a beetle, so as to test the principle of
the process. There is nothing like giving everything (unless it is
manifestly absurd) which is set forth as an improvement, a fair trial,
and this is the reason why we have presented the foregoing information,
in order that it may be tested by some of our tanners to see whether it
has any merit or not.
TANNING BUCKSKIN.
We present the following simple process for preparing buckskin.
The Indians have long been distinguished for making an exceedingly good
and durable buckskin.
One day a friend of ours (one of the best practical tanners and leather
dressers in the United States) watched with great earnestness, the mode
by which the squaws dressed their deer skins. He observed that they used
the brains of the deer mixed along with ley made of wood ashes forming a
kind of soap. This solution was rubbed on the skins, allowing them to
dry at each operation—two or three times, until the skins were
completely saturated with the solution. After this the skins were
smoked, the same as hams, in a pit dug in the ground. The idea suggested
itself to our friend, that there was no use of wanting shoes when there
were plenty of deer killed; but from a distance in the woods they could
not, and were not accustomed to bring the brains of the animal; but a
remedy was at hand; he knew that soap was the same composition, as that
used by the Indians in tanning, and he had plenty of that.
After the skins were properly prepared, a strong solution of warm yellow
soap was made up, in which they were handled until cold; they were then
dried and went through the same process until the practical tradesman
saw that they were made into leather; when they were afterwards smoked
in the manner of the Indians. From these operations an excellent
buckskin was made, which through the drenching of rains and the frequent
immersions in the swamps and everglades, retained its pristine softness
and qualities. Thus, in the wilds of Florida, a scientific tradesman
applied his knowledge and art, in a manner for which many had reason to
be thankful. In such situations the mechanic rises far above the
philosopher.
NEW METHOD OF TANNING.
A process was discovered in Rochester, New York, in 1850, by which
leather could be tanned in the short space of two hours. This is a “fast
age,” and “wonders” are now every-day occurrences. Formerly it required
_fifteen months_ to properly tan and finish leather. The leather here
referred to, was tanned by the “Journeymen Shoemakers Association” of
Rochester.
If this discovery is all that it is stated to be (of which we have some
doubts), viz., to make leather _equal to the French_, in such a short
time, it must be one of the most valuable discoveries of the age. As the
process, however, is not laid down in black and white, every man is
justified in suspecting its reality. A new process, however has come
into our possession lately, which is said to tan leather better and in
less time than by the old process. We give it for what it is worth.
Those in the art can make experiments for themselves—the only way to
test its merits. Three liquors are made up, 1st. One made of 20 pounds
of alum, and 20 of the sulphate of potash, and ten of the muriate of
soda, all dissolved in warm water. 2d, 100 pounds of catechu, dissolved.
3d. 4 pounds of alum, 2 lbs of the muriate of soda, dissolved. For a
hundred calf skins in a vat of sufficient size, put one fifth of No. 1;
viz., 4 pounds of the alum and potash and 2 of the muriate of soda,
(common salt)—then add one-tenth of the No. 2 solution, and one fourth
of No. 3. With this mixed solution enough of water is put into the vat
to cover the 100 skins and the temperature is kept up so as the hand can
bear it well. Men with poles rounded at their ends stir the skins for
about one hour, when they are taken out. They are then placed in another
vat of the same kind of solution, and the same strength, and stirred
frequently for about three hours, and let stand till next morning. They
are then removed, and one fifth of No. 1 mixture, and one-fifth of No. 2
added, when the skins are returned to the vat, stirred frequently, and
dripped every day for five days, when all the liquors of the solutions
should be taken up, and about 20 pounds more of dissolved catechu is to
be added. The skins are to be tried frequently, and more catechu is to
be added if necessary, and at the end of four or five weeks the
operations will be completed.
DEXTER’S PROCESS OF TANNING.
A few years since, Mr. J. D. Dexter, of Albany, N. Y., discovered a
process of tanning, which he claims to be an important improvement. The
main feature of the invention consists in a compound of chemicals, by
which not only time, money and labor are saved, but the leather thus
prepared, possesses more strength than that manufactured in the old way.
This compound is called “Dexter’s Electric Process.”
A sheep, calf, goat or deer skin is taken in a green state, and in from
eight to ten days it is manufactured into leather and is ready for
market. From four to six days are consumed in preparing a skin for
tanning, in the removal of the wool, hair, &c.; it is then thrown into a
tub, and washed in three chemical preparations, which takes from one to
two minutes; it is then taken out and dried, and in twenty-four or
forty-eight hours after it is taken from the tub it is ready for market.
The time occupied in drying depends much upon the weather; but after it
is thoroughly dried it can be finished in about twenty minutes or half
an hour. Under the old system of tanning, it takes from three to four
weeks to prepare the skin, and from three to six months to bark tan and
finish it.
By the discovery of this new process, a skin is converted into leather,
in as many days as it takes months to bark tan, and besides, it is not
only stronger and more durable, but the leather is made water-proof.
They can manufacture sheep-skins by this process, into leather, in six
or eight days, which not only resembles calf-skin, but for boots and
shoes it is preferred by those who have worn them, on account of its
being more durable, and softer than calf manufactured in the old way. By
this method of tanning, there is a great saving. One hundred sheep-skins
can be tanned for 37 to 50 cents, while to bark tan them would incur an
expense of at least $6.
Patent leather is manufactured out of sheep-skins, which is said to be
more durable and less liable to crack than that made of bark-tanned
leather.
FAIR LEATHER.[5]
This leather, used for the soles of ladies’ shoes, is made, preferably,
from hides tanned with Spanish oak. After having been soaked and
scoured, they are separately spread upon a clean table and sponged on
the grain side with the following mixture, reduced by dilution with
water.
Footnote 5:
Morfit’s Theory, Chapter L.
The proportions for nine and a half pints, which is the quantity
required for twenty-five sides, are
Crystalized Chloride of Tin, 8 oz.
Muriatic Acid, free from Iron, 4 fluid oz.
Sulphurized Ether, 8 fluid oz.
Alcohol, 32 fluid oz.
Water, 40 fluid oz.
The tin salt is placed in a blue stone jar, with the acid, and the whole
is stirred until perfect solution is effected. The ether, alcohol and
water are then added and stirred in successively.
This process, patented by Prof. J. C. Booth, of Philadelphia, is founded
strictly upon scientific principles. The tin, salt and acid, are the
bleaching agents, while the alcohol, ether and water are dilutants as
well as protectives against any destructive agent of the former. Its
whitening effect extends throughout the hide, and is not limited merely
to the surface. After the application of the liquor, the leather is
oiled, dressed and rolled, as in the usual currying process.
This mixture is not applicable to leather tanned with black oak-bark, as
it colors it yellow.