GLOVE-KID.
This branch of leather manufacture is mainly carried on in Germany,
Austria, and France. In Germany and Austria, lamb-skins are principally
employed; in France, kid-skins. For fine gloves, the skins of very
young animals only can be used. The ordinary style of manufacture is as
follows:--The soaking of the dried skins is effected in large wooden
tubs (_Kufen_, _Bottichen_), and occupies on the average 3-4 days,
according to the character of the soak-water, the size of the skins,
and the time they have been stored. The skins, when thoroughly and
uniformly softened, are unhaired, either by painting the flesh-side
with a thin paste of lime, or in lime-pits. In unhairing by painting
(_Schwöden_), the skins, after coating the flesh-side with lime, are
folded together, so that the lime comes as little as possible into
contact with the wool, and these bundles or "cushions" are placed in
a tub, in which they are most frequently covered with water. After
unhairing on the beam with a blunt knife, the skins must be limed for
some days, in order that the leather may stretch well, a quality which
the Germans denominate _Zug_. By this method of unhairing, the wool
is preserved uninjured, but it is not suitable for the finer sorts
of leather. The unhairing in lime-pits is done either with gas-lime
(Grünkalk), or, as is now almost exclusively the practice, with the
so-called "poison-limes" (_Giftäscher_). These are prepared by mixing
red arsenic (arsenic sulphide) with lime, while it is being slaked, and
is at its hottest. The calcic sulphydrate (and perhaps sulpharsenite)
thus formed hastens the unhairing, and gives the grain a higher gloss.
Well-conducted establishments now avoid as much as possible the use of
old limes, which produce a loose, porous leather, with a rough, dull
grain. The liming lasts on the average 10 days, and is of the greatest
importance. It is essential that the interfibrillary substance shall
be dissolved, that the leather may have the quality known as _Stand_,
that is to say, may be strongly stretched in either length or breadth
without springing back. It also depends upon the liming (and this is of
special importance in the case of lamb-skins), whether the tissue of
the fat-glands is well loosened, so that the fat, either as such, or as
lime- or ammonia-soap, may be readily and completely worked out. Skins
in which this is neglected can never be properly dyed.
When the hair (or wool) is well loosened, the skins are rinsed in
water, and then unhaired on the beam with a blunt knife. The water
employed in washing should not be much colder than the limes, or it
will prevent the hair from coming away readily. The wool or hair is
washed and dried for sale. The skins are thrown into water, to which a
little lime-liquor has been added, to prevent precipitation of the lime
in the skins by the free carbonic acid of the water, which would have
the effect of making them rough-grained.
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.
This is prepared by soaking wheaten bran in cold water, diluting with
warm water, and straining the extract through a fine hair-sieve.
Sufficient of the liquid must be employed to well cover the skins, and
the temperature may range from 50° F. (10° C.) to 68° F. (20° C.).
These conditions are favourable to bacterial activity, which comes
into play, and, on the one hand, evolves formic, acetic, lactic, and
butyric acids, which dissolve any remaining traces of lime, and on the
other, loosens and differentiates the hide tissue, so as to fit it
to absorb the tawing solution (_Gare_). Much care is required in the
management of the bran drench, especially in summer, since the lactic
readily passes into the butyric fermentation (see also p. 186). The
tawing mixture is composed (like that employed in the fabrication of
calf-kid, q. v.) of alum, salt, flour, and egg-yolks, in a quite thin
paste. The skins are either trodden in it with the feet, or put into
a tumbler-drum with it (Fig. 48). Kathreiner pointed out, some years
since (in vol. i. of 'Der Gerber'), that a mixture of olive-oil and
glycerine might be partially substituted for the egg-yolks, in both the
tanning and dyeing of glove-kid leather.
The tawed skins are now dried by hanging on poles, grain inwards.
Rapid drying in well-ventilated, but only moderately-heated, rooms is
essential to the manufacture of a satisfactory product.
[Illustration: Fig. 59.]
[Illustration: Fig. 60.]
The dry leather is rapidly passed through tepid water, and after being
hung for a very short time, to allow the water to drain off, is trodden
tightly into chests, and allowed to remain in them for about 12 hours,
so that the moisture may be uniformly distributed. It is then trodden
on hurdles (_Horden_), composed of square bars of wood, joined corner
to corner, so as to make a floor of sharply angular ridges, Fig. 59.
The next operation is stretching over a circular knife, called the
_Stollmond_ (_stollen_, Eng. "staking"), shown in Fig. 60; then the
leather is dried nearly completely, and staked again.
Dyeing.
The dyeing of glove-kids is done in 2 ways:--_a._ The skins are plunged
into the dye-bath (_Tunkfarben_). In this way, all light colours are
ordinarily produced, such as _gris-perle_ (pearl-grey), _paillé_
(straw-yellow), _chamois_ (reddish yellow), silver-grey, aquamarine,
&c. _b._ The skins are spread on an inclined or rounded table of stone
or metal, and brushed over, on the grain side, first with a mordant
(_Beize_), then with the dye-liquor, and lastly, with a solution of
a mineral salt (Plate 7). The mordant serves to fix the colour on
the surface of the skin, to prevent its striking through, to produce
certain modifications of colour, and to enable any parts of the skin
which yet contain fat to take the colour evenly with the rest. To
satisfy these conditions, the composition of the mordants is very
varied. Potash bichromate, ammonia, potash, soda, and stale urine are
among the most frequently employed, seldom separately, but usually in a
mixture containing 2 or more.
Dye-stuffs of vegetable origin have always held the first place. Those
most in use are logwood (_Blauholz_), Brazilwood (_Rothholz_), the two
fustics--_Cuba Gelbholz_ (_Morus tinctoria_) and _Ungarisches Gelbholz_
(_Rhus cotinus_), several species of willow-bark and of berries,
indigo-carmine, and indigo dissolved in sulphuric acid.
Aniline colours used alone remained in fashion for a short time only,
but are now usefully employed as top-colours (_Ueberfarben_), viz.
brushed in very dilute solution over vegetable colours. In this way,
particularly tasteful shades of green, violet, and marine-blue may be
produced.
After the mordant has been applied once or twice, and the colour
3-6 times, a wash (_Ueberstrich_) containing some metallic salt is
generally applied, with the object either of bringing out the special
tone required, or of making the colour more lively and permanent.
The so-called "vitriols" are mostly employed: "white vitriol" (zinc
sulphate), "blue vitriol" (copper sulphate), "green vitriol" (iron
sulphate), and occasionally other salts.
Before dyeing, the greater part of the flour, salt, and alum must
be removed from the skins by washing with tepid water; and they
therefore require a second feeding (_Nahrung_) of egg-yolk and salt.
In the case of the skins which are dyed by plunging into the dye-vat
(_Tunkfarben_), this is done after the dyeing is completed; in that of
brush-dyeing, before the dyeing process.
After the dyeing, the skins, if dipped, are wrung out; if brush-dyed,
sleeked out with a brass plate, to get rid of superfluous water. They
are then dried in an airy room. Before staking (stretching), the skins
are laid or hung in a damp cellar, or in moist saw-dust. They are
staked twice: once damp, and once nearly dry.
Skins which are much damaged on the grain, or otherwise faulty, are
smoothed with lump pumice on the flesh-side, either by hand or machine.
They are then dyed on this side, mostly by dipping, but occasionally
with the brush, in which case, the method described is slightly
modified.
Indebtedness is acknowledged to F. Kathreiner, of Worms, and David
Richardson, of Newcastle, for much information on the production of
light leathers. The Plates 1 to 8 represent the works of Messrs.
Tréfousse et Cie., at Chaumont (Haute-Marne).