There are two kinds of silk (1) raw silk (reeled silk, thrown silk,
drawn silk), and (2) waste silk or spun silk.
Raw silk is that directly taken from the cocoons. Waste silk is the
silk from cocoons that are damaged in some way so that they cannot be
reeled off direct. It is, therefore, carded and spun, like wool or
Silk in the raw state is covered with a silk gum which must be boil
off before dyeing is begun. It is tied up in canvas bags and boiled up
in a strong solution of soap for three or four hours until all the gum
is boiled off. If it is a yellow gum, the silk is wrought first in a
solution of soft soap at a temperature just below boiling point for
about an hour, then put into bags and boiled. After boiling, the soap
is well washed out.
Generally speaking, the affinity of silk for dyes is similar but
weaker in character to that of wool. The general method for dyeing is
the same as for wool, except, in most cases, lower temperatures are
used in the mordanting. In some cases, soaking in a cold concentrated
solution of the mordant is sufficient. The dyeing of some colours is
also at low temperature.