CALF-KID.
Calf-kid is used for light upper-leather, and belongs to a different
class from any yet described, being "tawed" instead of tanned. In this
respect, and in most details of its manufacture, it resembles glove-kid.
The process is as follows. Selected calf-skins, dried or salted, are
the raw material, and after a suitable softening in fresh water, are
limed for 2-3 weeks, or till the hair goes easily. They are then
unhaired and fleshed in the usual manner, pured with a bate of dogs'
dung, scudded, and again cleansed with a bran drench. In Germany, the
bran drench is used alone, and is composed of 33 lb. bran to 100 medium
skins. Before use, the bran should, especially in summer, be well
washed, to free it from adhering meal. The temperature of the drench
should not exceed 100° F. (38° C.), and the skins should remain in for
8-10 hours. Lactic acid is produced by fermentation; this removes lime,
and is itself neutralised by the products of putrid fermentation which
succeeds it.
The tanning is accomplished in a drum with a mixture of alum and salt;
and after drying, the skins are again moistened, and worked in the
drum with a mixture of oil, flour, and egg-yolk. In the German method,
these two operations are combined. Eitner, who has written a series of
articles on the process, gives 40 lb. flour, 20 lb. alum, 9 lb. salt,
250 eggs, or about 1-1/3 gal. of egg-yolk, 7/8 pint (1/2 litre) of
olive-oil, and 12-16 gal. water, as a suitable mixture. The skins are
worked in a drum-tumbler (preferably a square one, see Plate 5) for 20
minutes, then allowed to rest 10 minutes, and this process is twice
repeated. The temperature must not exceed 100° F. (38° C.), and it is
said to be important that the drum should be ventilated by holes at
the axis.
The skins are allowed to drain, are then rapidly dried at a temperature
of 140°-160° F. (60°-71° C.), and, after "samming," or damping with
cold water, are staked by drawing them to and fro over a blunt knife
fixed on the top of a post (see Plate 6). They are then wetted down and
shaved, either with the moon-knife or ordinary curriers' shaving-knife,
and sometimes receive a second dressing of oil, flour, and egg, to
soften them still further.
Dyeing black is accomplished either by brushing on a table, or by
"ridging" or folding, grain-side outwards, and drawing quickly through
baths of the mordant and colour. To prepare them for the colour,
stale urine is generally employed. A deeper colour, and one less
liable to strike through the skin, is obtained by adding 1/4 lb.
potash bichromate to 4 gal. of urine, or the following mixture may be
substituted with advantage, viz. 1/2 lb. Marseilles soap dissolved in
boiling water, 5 or 6 egg-yolks added, and the whole made up to 4 gal.
with water and 1/4 lb. potash bichromate. The colour used is infusion
of logwood or its extract, or two-thirds logwood, which is best
extracted by stale urine or old soak-liquor, with addition of a small
quantity of soda (1 lb. to 25 lb. dye-wood). It is fixed and darkened
by a wash of iron-liquor (1 of iron protosulphate in 75 of cold water).
After being again dried, the skins are grounded with the moon-knife,
and rubbed over on the grain with a composition containing oil, wax,
&c., and are finally ironed with a flat-iron, to give them a fine and
smooth surface. Eitner gives a recipe for the gloss:--1 lb. gum arabic,
1/2 lb. yellow wax, 1/2 lb. beef-tallow, 3/4 lb. Marseilles soap, 2
lb. strong logwood infusion, and 1 gal. water. The water is brought to
a boil in an earthen pot, and then the soap, wax, gum, and tallow are
added successively, each being stirred till dissolved before adding the
next, and lastly the logwood. After boiling for an hour, it is allowed
to completely cool, being incessantly stirred during the whole process.