LEATHER INFORMATION

LEATHER INFORMATION
History of Leather: From early settlers to modern
day people Leather has been used as a durable
and flexible material serving countless purposes.
Early settlers in America found the native peoples
were skilled in the art of leather tanning especially
buckskin which is exceptionally soft and water-
resistant. The technique was to pile the skins
until they began to decay; the decay loosened the
hair which was removed by hand along with the
flesh from the underside. Oil and animal brains
were pounded into the skins, following which they
were often smoked. During colonial times, leather
enjoyed a range of uses including door hinges, fire
buckets, tableware and coach springs. The oak-
bark method from thousands of years before was
used until the end of the 18th century when
people learned that bark from hemlock, chestnut
trees and other plant substances could also be
used for tanning leather.
Come the end of the 19th century, an American
chemist discovered that chromium salts used on
hides produced a different kind of raw hide
leather, than produced by the traditional bark-
tanning method. The new procedure required the
resulting leather to be treated with soaps and oils
and has become the leading modern method for
producing leather. Chrome tanning produced
softer more supple leather than vegetable tanning,
suitable for the increasing demand for lightweight
and fashionable footwear and reflecting our new
way of living after the invention of the
automobile. The process begins in rotating drums
with a bath in a chemical containing trivalent
chrome. It usually takes eight hours for the
chrome to penetrate all the way into the hide.
Once this has been achieved the chrome is “fixed”
by adding an alkaline chemical such as sodium
carbonate or bicarbonate. After this treatment the
hide is considered tanned. Chrome tanning is
used in 90% of leather manufacture today.
Vegetable tanning is still used in shoe soles,
luggage, saddlery, belt leathers and some
upholstery. The process is slower than chrome
tanning and involves the chemical substance
tannin, or tannic acid, which is extracted from the
barks of trees. This process is normally
performed in drums taking two to four days.
After tanning, wringing lowers the moisture
content of the hide in preparation for splitting.
Depending on the end use of the leather product,
the hides are split into sheets of the required
thickness and processed further through a
shaving machine for added quality. Around the
end of the 19th century, Americans also invented
machinery to make the job of leather production
easier, including one which could split leather to
any desired thickness, thereby increasing output.
Machines were also invented that would speed up
de-hairing, fleshing and cleaning. After shaving,
chrome tanned hides are again placed in rotating
drums with hot water, dyes and synthetic tanning
materials to obtain the desired color. They are
then lubricated with natural fat or synthetic fatty
type chemicals, or a combination of both to
obtain the softness required by the final product.
The next process is setting, which is the removal
of excess water and spreading the hide out prior
to drying. Upholstery leather is normally toggle
dried (spreading the leather over expanding
frames held by “toggles” or clips) hence the clip
marks around the entire hide. Staking is the
mechanical softening of the leather after drying.
The hides may also be softened by milling which
is dry tumbling with atomized moisture injected
into the tumbler. Finishing consists of placing a
series of coatings on the surface of the leather.
These coatings are designed to protect the
leather and produce surface effects pleasing to
the eye and hand. Some finishing processes apply
plastics such as acrylic and urethane resins.
Others coat with vinyl, wax, nitrocellulose, or dye.
Various mechanical operations are necessary to
obtain the desired effect. Hydraulic presses,
printing, embossing machines, automatic spray
applicators and vacuum driers are a few of the
machines used in the finishing process. Patent
Leather In 1818, Seth Boyden of Newark, New
Jersey, invented patent leather after investigating
ways to treat leather that would render it dressier
than the classic form while retaining its durability.
Althouth Seth's process employed a linseed-oil
based lacquer coating to give the leather its shiny
finish, today patent leather is usually coated in
plastic. Patent leather is an eye-catching, water-
resistant material reserved for fashion items such
as wallets and handbags, shoes, and trench
coats.
Dyeing leather holds dye well due to its porous
nature. Before the mid-1800s, all dyes were
created from vegetable matter. Since then, dyes
have been produced using coal-tar or petroleum.
Traditionally seen in only black or brown, leather
jackets today are dyed in every color imaginable .
Types of leather: Steer hide is pebbly and crinkly
in texture and very pliable. It comes in natural or
two-toned colors. Cowhide is versatile and
natural in color with a smooth grain. Sheep is
medium-weight and not as durable as other
leathers. Morocco goat is used for linings,
billfolds, and book bindings and comes in several
colors. Pigskin is durable, comes in a natural
color and varies in weight. Suede is a type of
finish which is generally made on sheep skins.
Suede is available in many colors, and is popular
for garments as well as linings.
Leather as a fashion statement . Today, at least
half of leather is used in footwear, one-quarter in
clothing, only 15% in upholstery, and the
remainder in small leather goods. Leather is also
used in cars, planes, and equestrian saddles. The
leather jacket, used in the military and by aviators
(called “bomber jackets”) during World War Two,
became a fashion item in the 1950s. After Marlon
Brando wore one in The Wild One in 1953, the
black leather jacket took on iconic status,
representing rebellion and everything “cool”. The
leather jacket worn by Fonzie in the Happy Days
sitcom became so famous that it now enjoys
pride of place at the Smithsonian Institute in
Washington. Toward the end of the 20th century,
the iconic bomber jacket was joined by the
leather coat worn by Arnold Schwarzenegger in
the Terminator franchise and Keanu Reeves'
leather trench in The Matrix.