The Opelousas courier., 1883-11-03
Sole Leather.

anu 1lSIlUS uIS Ill.,
Sole Leather.
There are two methods generally
followed in preparing sole leather,
which illustrates the principle adopted
by all tanners. These are commonly
called the "acid" and "non-acid
processes. In both methods it is acid
that pumps the hide and distends its
fibers for the reception Of the tan
liquor. In the former process, how
ever, a mineral acid is used, either
alone, with a large proportion OF
water, or in connection with more or
less of the vegetable acid furnished by
the old, sour liquors, to hasten the
process of preparing the hides for the
tanning proper; while, by the latter
process, the hides, after being UNFAIR
ed, are handled for several days in the
old, sour liquors, but without the aid
of the mineral acid (Which almost in
yariably consists of vitriol or sulphuric
acid) to effect the same object; that is,
distend the fibers and open the
pores. In using the vitriol great
care must be observed in the
first stages, or the leather will
be very dark, and have what is called
a very poor grain, i. e., will not make
a light-colored bottom for boots and
shoes, an object which is very much
sought after in all sole leather. The
leather is also more likely to be hard
and brittle than that prepared by the
non-acid method. The old liquors used
in the latter method are simply the
tanning liquors which have become
weak by use, and in which the remain
ing tannic acid has largely been chang
ed to gallo acid by exposure to the air.
The grinding Of the bark aud the
making of the liquors therefrom is a
most important part of the work. The
bark is stripped from the tree and cut
in pieces four feet long; a month OF
two is generally sufficient to make it
dry enough to grind, though, if kept
two years in a large close pile, and not
much exposed to wet, it will not be
materially injured. 1t is ground in a
large mill, not unlike a coffee mill in
principle, and about the size of a grain
of wheat is considered the proper de-
gree of fineness.
To get the tanning principle from
the ground bark, teaching with hot
water is prejudicial, for in that way
resin and coloring matter are also ex-
tracted, and teaching with cold water
does not extract all the tannin. Both
modes are used.
Leaching with hot water, or
swelling the ground bark with steam
before teaching, causes the leather to
be darker than that made with liquors
which are leached cold. The watts in
which the hides are handled and laid
away in tanning are Of various sizes,
either large enough for whole hides or
for sides, and are about six feet deep.
In handling, the hides are sometimes
sewed together at the ends, so that
they can be reeled from one vat to
another but this is only to facilitate
the work in the frequent changes
that have to be made. For the
first few days the hides are chang
ed every two or three hours
from n liquor to another, the first
liquors. being very weak, and the last
liquors in which the hides are thus
handled, at the end of 10 or Is days.
having 10 or IL degrees of strength.
From the handlers the hides are placed
in what are called layaway watts, a
shovelful of ground bark on the top of
each hide, and the whole covered with
the bark liquor. At this point the
customs in Europe and America vary.
In this country it is laid away half a
dozen times, the strength Of the liquor
being increased with each layaway, be-
ginning with the liquor Of 10 degrees
and the time from one to two weeks;
and increasing to % degrees or 80 de-
grees, and even more at the last, and
the time being from six weeks to two
months, according to the judgment of
the tanner. It win thus be seen that
in this country it requires at least four
months for that manipulation of sole
leather which may be strictly called
tanning.
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