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The
two tanning agents differ from one another only in the
form they are delivered and in their concentration and
there fore only Jktan DI is referred to in the following
text. The amount indicated apply to the powder type; if
the liquid is used the amount recommended here must be
double.
Jktan
DI can be used as a replacement tanning agent in all
stages of tannage for the production of heavy, medium
and light leathers. Calculated on the pure tan content
upto 25% of the total vegetable tanning employed may
generally be tanning agent e.g. 10-15% for sole leather,
and upto 15% for bag and upholstery leather, russet and
harness leathers, and light leather types.
Jktan DI may also be used, either alone or in
combination with vegetable tannins, for the retannage of
chrome leather and in the production of corrected grain
leathers which are to be dried by pasting or vacuum.
It imparts good fullness, a lighter colour and a
resilient grain to the leather Prior to retannage, the
leather should be partially neutralized with about 1-2%
of Jktan FC. It has often been found beneficial to
prefatliquor the leathers with sulphonate / sulphited
oils. Dyeing may be carried out before retannage.
For a light retannage, 2-3% of Jktan DI is used based on
the shaved weight. It is often advisable to carry out
the retannage at temperatures of 40-50oC. Therefore, if
the leathers are predyed retannage can be carried out in
the same bath after the dyestuffs have been taken up by
the leather. In this method, the dyebath should not be
acidified. In the retannage of semichrome leather
40-50% of the normal amount of vegetable tannin
calculated as pure tan, is replaced by the corresponding
quantity of Jktan DI.
In
the production of light leathers, such as bag upholstery
and sandal leathers, the use of Jktan DI is beneficial,
because it imparts to the leather a particularly soft
handle and an appreciable pale shade. |
