There are three general method of application of mordant
dyes as mentioned below:
1. Chrome
mordant process
2. After-chrome
mordant process
3. Meta
chrome or chromate mordant process
Now they are shortly described below:
1 ) Chrome mordant
process:
This is a two bath process. In this process at first
material is impregnated with an insoluble chromium hydrate and then dyeing is
done a separate bath.
2
) After-chrome mordant process:
This is the oldest and the most common mordant dyeing
process. Here the material is first dyed with an acid dye and then mordanting
with chromium is carried out in a separate bath. Or mordanting can be done in
the same bath after exhaustion of the dye has been completed.
3 ) Meta chrome/chromate mordant process:
In mete chrome
process, dyeing and mordanting are carried out simultaneously in the same bath.
Here the mordant is present in the form of chromate which does not form the
lake with the dye and which is generally converted into dichromate. The pH of
the bath is kept around 6-7.This method has the advantage of facilitating
shading and requires less time, then the after-chrome process. It gives highly
level of residual chromium in the effluent. This method is now almost obsolete