We all know that leather is the skins of animals, dressed and prepared
for our use by tanning, or some other process, which preserves them from
rotting and renders them pliable and tough.
The larger and heavier skins, such as those of buffaloes, bulls, oxen,
horses and cows, are called “hides;” while those of the smaller animals,
such as calves, sheep, pigs and goats, are called “skins.”
[Illustration: SCOURING]
The tanning of raw hides taken from animals is an ancient trade. The
bark of trees made into a liquor has been used for centuries in treating
practically all kinds of hides.
The oak, fir, hemlock and sumach are the most familiar of the many trees
from which “tannin” is obtained for this purpose.
The cow hide is used practically altogether for sole leather and is bark
tanned in the majority of cases. After the hide is taken from the animal
it is either dry cured, or else salted green, and packed for shipment or
storage.
The first process of preparing sole leather is to cut these hides in
half or sides. The sides are then run through lime vats for the purpose
of loosening the hair. They are then run through the unhairing machine,
in which large rollers remove the hair.
From the unhairing machine the hides pass to a fleshing machine, which
cuts away all the flesh or fat on the hide. They are then trimmed and
scraped by hand, after which the real tanning process begins.
The old method of tanning leather was in large vats, which were filled
alternately with tan bark and hides, then filled with water and allowed
to soak for a period of eight to nine months before the tanning process
was complete. The extract of bark in liquor form is used today by all
large tanneries.
After the hides have been all prepared for tanning they are hung on
rockers in the tanning vats, where they are kept in motion both day and
night so that all parts of every hide are equally tanned. They are
changed from time to time from weaker into stronger liquor until the
tanning process is complete.
[Illustration: TANNING VATS]
All sole leather is filled more or less to make it wear the better.
The drying process comes next. The hides are all hung in a dry loft,
where artificial heat of different temperatures is used until they are
thoroughly dry. The drying of the hide is as important as the tanning.
Hides that are dried too quickly become brittle, so that great care must
be taken in this drying process. Even the weather conditions play an
important part.
[Illustration: ROLLERS]
After the hides are thoroughly dried they are then oiled and ironed by
large rollers having several hundred pounds pressure. This gives the
grain side of the leather a finished appearance and also serves to press
the leather together compactly.
[Illustration: RUBBING]
Before this leather can be cut into sole leather it has to be again
dried and properly edged to secure the best results.
[Illustration: BOARDING ROOM]
Bark-tanned leather that is used for upper stock in shoes is tanned
practically the same way as the bark sole leather, except lighter hides
are used and the finishing processes are of a nature to make it softer
and smoother.
The above tannage is what is called vegetable tannage. There is also a
tannage made from minerals that is called chrome. This is used mostly in
tanning soft, glovey upper leather, which when finished makes a very
tough yet soft and pliable leather for footwear.
Ninety to one hundred days are required to tan bark leathers, while the
chrome tannage is very quick and on the average requires only about
three weeks.
The brilliant smooth surface of patent, enameled, lacquered, varnished
or japanned leather is due to the mode of finishing by stretching the
tanned hides on wooden frames and applying successive coats of varnish,
each coat being dried and rubbed smooth with pumice stone. There is also
a process called “tawing,” which is employed chiefly in the preparation
of the skins of sheep, lambs, goats and kids. In this process the skins
are steeped in a bath of alum, salt and other substances, and they are
also sometimes soaked in fish-oil. The more delicate leathers are
treated in this manner, those especially which are used for
wash-leathers, kid gloves, etc.
[Illustration: MEASURING]
In currying leather for shoes the leather is first soaked in water until
it is thoroughly wet; then the flesh side is shaved to a proper surface
with a knife of peculiar construction, rectangular in form with two
handles and a double edge. The leather is then thrown into the water
again, scoured upon a stone till the white substance called “bloom” is
forced out, then rubbed with a greasy substance and hung up to dry. When
thoroughly dry it is grained with a toothed instrument on the flesh side
and bruised on the grain or hair side for the purpose of softening the
leather. A further process of paring and graining makes it ready for
waxing or coloring, in which oil and lampblack are used on the flesh
side. It is then sized, dried and tallowed. In the process the leather
is made smooth, lustrous, supple and waterproof.
* * * * *
What is a “Glass Snake”?
“Glass snake” is the name which has been given to a lizard resembling a
serpent in form and reaching a length of three feet.
The joints of the tail are not connected by caudal muscles, hence it is
extremely brittle, and one or more of the joints break off when the
animal is even slightly irritated.