1st.—The wool is boiled first with the mordant and then in a fresh bath with the dye.
2nd.—The wool is boiled first with the dye, and when it has absorbed as much of the colour as possible the mordant is added to the same bath, thus fixing the colour.
A separate bath can be used for each of these processes, in which case each bath can be replenished and used again for a fresh lot of wool.
3rd.—The wool is boiled with the mordant and dye in the same bath together. The colour, as a rule, is not so fast and good as with a separate bath, though with some dyes a brighter colour is obtained.
4th.—The wool is mordanted, then dyed, then mordanted again. This method is adopted to ensure an extremely fast colour. The mordant should be used rather sparingly.
SILK
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 cotton.
Silk in the raw state is covered with a silk gum which must be boiled 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.