A Text-book of Tanning: A treatise on the conversion of skins into leather, both practical and theoretical.Procter, H. R. (Henry Richardson)
Science
A Text-book of Tanning: A treatise on the conversion of skins into leather, both practical and theoretical.
Procter, H. R. (Henry Richardson)
Tanning
Next comes the first fleshing (_Vergleichen_) or "levelling." By this,
the loose cellular tissue on the flesh-side is removed, together
with the head, ears, and shanks, and the flanks are trimmed. The
skins are then again thrown into water, softened with lime-liquor as
above described, and then into a bate of dogs' dung. This is prepared
by stirring up white and putrid dogs' dung with boiling water, and
straining it through a sieve or wicker basket. The bate must be used
tepid, and not too strong. The skins "fall" (lose their plumpness) in
it rapidly, and become extremely soft and fine to the touch; and the
fat-glands, remaining hairs, and other dirt, can now be very readily
scudded out. So far no completely satisfactory substitute has been
found for this somewhat disgusting mixture, but it has been noted that
guano will produce similar effects. With regard to the mode of action
of the dung bate, much has been speculated without proof, and exact
analytical evidence is wanting; but, no doubt, a weak putrefactive
action goes on, as may be deduced from the presence of _bacteria_;
further, the ammonia and weak organic acids present in the putrefying
dung are capable of acting on fat and lime; and finally, a direct
mechanical effect seems to be produced, difficult to describe, but
favourable to the succeeding manipulation. Too strong bates, or too
long continuance in them, produces evident putrefactive effects on the
skins. (See also p. 184.)
When the skins come out of the bate, they are stretched and worked
(_abgezogen_) on the flesh with a sharp knife, and any remaining
subcutaneous tissue is removed. This constitutes the second
fleshing. They are then rinsed in warm water, and beaten with clubs
(_Stoss-keule_), see Plates 3 and 4, in a tub, or worked in a
tumbler-drum (_Walkfass_), in either case with a very little water
only; and finally brought into a tank of water, not too cold, and kept
in constant motion with a paddle-wheel.
The skins are next cleansed on the grain-side by working on the beam
with plates of vulcanite with wooden handles, so as to remove fat,
lime- and ammonia-soaps, and other lime compounds, together with all
remaining hair or wool. The skins are now a second time washed in the
"paddle-tumbler," first in cold, and then in tepid water; and after
allowing the water to drain from them, they are transferred to the bran
drench.
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