Leather: From the Raw Material to the Finished ProductAdcock, K. J.
History
Leather: From the Raw Material to the Finished Product
Adcock, K. J.
Leather
A quick and effective method of deliming is to treat the skins
in a weak solution of lactic acid. Some dressers use a drench of
pea-flour or bran. The mild acids produced by the fermentation of
these materials not only neutralise the lime but also reduce the
gristly nature of the skins to a soft, supple condition. The bran
infusion is slightly warmed to hasten the process of fermentation,
but the temperature must not exceed 100° F. (32° C.). The linings
are then rinsed in cold water and sent to the stocking machines,
in which they are kneaded until they become quite soft. Either the
faller-stocks or the mechanical pushers (Fig. 14) may be used, the
latter being the more modern machine. The operation may require from
four to ten hours, the completion being determined by the condition
of the skins. "Samming" follows stocking, and for this purpose the
linings are hung up in the drying shed until thoroughly dripped, but
not dried. In this slightly damp condition they are then prepared
for the next process of oiling, which is the most important part of
chamois-dressing, as it converts the perishable raw linings into
leather. In the United Kingdom, cod oil (generally Newfoundland) is
used exclusively, and gives best results. Whale and shark liver, or
menhaden oils are often used abroad.
The linings are placed in a tub or vat, a few at a time, and oil is
poured over each layer until a sufficient number has been treated
to fill the stocking machine. The stocks are run for half-an-hour,
or until the oil has penetrated the linings, when they are put
back into the vat, where they remain for about an hour. They are
then re-stocked, taken into the shed to samm, re-oiled in the vat,
and stocked again. These processes are repeated until the skins
are thoroughly impregnated with the oil, when they are dried in a
warm stove. The skins are not yet converted into leather, which
only occurs in oil-dressing, after the oxidation of the oil. This
is effected by spontaneous heat, the dry oiled skins being heaped
in boxes and covered. Strict attention has to be paid to avoid
over-heating the skins, which are turned over and changed at
intervals. When the leather ceases to heat, the process is completed.
It is then dipped into hot water and mechanically pressed, to remove
surplus or uncombined oil, which is collected and sold under the
name of "sod oil." The leather is afterwards drummed in warm water
and finely cleansed in an alkaline solution, potash, soda, or borax,
chiefly the first named, being used for this purpose. They are then
rinsed in water, dried, damped, and softened by staking. At this
stage, the best skins are sorted out for the glove makers. The
others are finished for wash-leather by re-staking, paring with the
moon-knife, and smoothing both sides of the skin with a scurfer, or
fine pumice-stone. In the warehouse, they are damped, stretched out,
piled up, and kept fully extended by placing heavy weights near the
edges of each pile of skins.
Public-domain text, read in full here on John Shaqi.
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