necessary to shorten the process and to use sulphide, this should be
added only to the tail liquors of the round, and with it should be
added, if possible, some calcium chloride to reduce the harshness of the
soda. The skins should be puered thoroughly to obtain the necessary
softness, bate-shaved if desirable, and drenched with 8 per cent. of
bran overnight.
In tanning for fancy work and for dark colours, the goods are coloured
off and evenly struck through with sumach liquors, and then tanned
further with liquors made from oak bark, myrabolans or chestnut extract.
The methods are very closely similar to those used for goatskins and
sealskins (Part II., Sections II. and III.), and need not be described
in further detail. The tannage is finished off in sumach. For
bookbinding work, however, a pure sumach tannage is given, using liquor
slightly warm (70° F.). Paddle tannages are common, but for bookbinding
the bag or bottle tannage is often preferred. The skins are sewn
together in pairs, grain outwards, and nearly filled with warm sumach
infusion, just as described for goatskins. They are then handled in old
sumach liquors for about 3 days, and piled to drain and press. At this
stage the bag is cut open, the goods worked on the flesh, and the
tannage is completed with separated skins in newer sumach liquors,
handling at least once a day for 4-5 days, as necessary.
In finishing there is the usual variety, but a plain ungrained finish is
most typical, as the smooth and fine grain of the young animal lends
itself to this type of finish better than the skins of goat and seal,
and gives a better quality leather than those from the sheep. The crust
skins are wet back with water at about 110° F., and, if necessary,
sammed and shaved. Sumaching follows, the operation being carried out in
a drum for 1-2 hours. The skins are then well struck out. Striking and
setting should always be thorough for a plain finish, and this case
forms no exception. Dyeing follows next, the paddle being often
preferred to the drum, which is liable to work up a grain. The dyed
skins are placed in cold water for a while and again well struck out.
They are often nailed on boards to samm, and are then set out, lightly
oiled with linseed oil and dried out in a cool shed. Seasoning follows,
with milk and water only. The operation may be done with either brush or
sponge, after which the goods are piled grain to grain and flesh to
flesh to regulate. They may be next perched to soften and fluffed if
desired. After top seasoning with milk, water and albumin the skins are
hung up for a while, piled to regulate and brushed, first lightly and
then more vigorously. They may be then oiled very lightly and dried out
in a cool stove to ensure a soft leather.
REFERENCE.
Bennett, "Manufacture of Leather," pp. 55, 84, 105, 201, 207, 303.
SECTION VI.--JAPANNED AND ENAMELLED LEATHERS
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