to remain one hour. The silk gains some
in weight in this operation by absorbing a quantity of the iron in the
bath. After having been dipped in the first bath three or four times,
it is ready for the soap and iron bath, in which it is repeatedly
immersed, the operation causing a deposit of iron-soap on the fiber
which adds to its weight, but at the same time does not lessen its
flexibility and softness. Eight dippings in the iron and soap bath
increase the weight of the silk about 100 per cent.

3. =Blue Bottoming.= The next operation is to dye the silk blue, which
is done by immersing it in a solution of potash. In this it is worked
for half an hour, when it acquires a deep blue color. It is then
taken out, and after rinsing is ready for the "weighting" operations.

4. ="Weighting" Bath.= A catechu bath is now prepared, in which the
silk is entered and worked for an hour, and then allowed to steep over
night. The result is that the blue on the silk is decomposed, and the
goods by absorbing the tannin in the catechu increase in weight from
35 to 40 per cent. This bath is the most important one in the dyeing
of "weighted" black silks, as the dyer can regulate the strength of
the bath by the addition of tin crystals so as to increase the weight
of the silk to an astonishing degree. The proportion of tin crystals
used is regulated by the number of iron baths that have previously
been given the silk; if two baths of iron have been given, 5 per cent
of tin crystals are used; if four baths, 10 per cent, and so on. The
action of these chemicals is somewhat complex. All that is known is
that by reason of some peculiar quality possessed by silk it is
enabled to combine with iron and tin, and that exposure to the air
after the baths fixes these chemicals permanently upon the fibers,
thus increasing their weight to almost any desired extent. Silk,
according to its quality and weight, will take up of these substances
from 50 to 200 per cent without creating much suspicion. Instances
have been known in which silk has been increased nine times its own
weight. All the operations thus far have had for their object the
weighting of the silk, although the blueing and the catechu baths have
some influence on the finished result. After these come the dyeing
operations proper, two in number, mordanting and dyeing.

5. =Mordanting.= A bath of iron liquor heated to 130 degrees F. is
provided. The silk is entered, worked well for one hour,