The types of dyestuff that are used by tanneries generally varies depending
on the product range needed along with the dictates of the fashion world. It
is a fact that each tannery uses between 50-100 or more different types of
dyestuffs.
The leather industry primarily uses anionic dyestuffs, that can be divided
in the following families:
- Acid dyes
- Direct dyes
- Mordant dyes
- Pre-metalled dyes
- Solubilised sulphur dyes
- Reactive dyes although a part of the anionic group of dyes but use
limited to a certain extent.
- Basic Dyes, its use is also limited.
If we see from the chemical point of view the dyes used are mostly Azo
dyes, Anthraquinone dyes and Triphenylmethanedyes. Commercially speaking,
popular Black dyes account for nearly 60-70% of all leather dyeing. Also,
out of this a dye variety called Acid Black 210 dominates with 80-90% usage
of all of the black dyes used.
Following are the few important tests that can be
undertaken for testing the colour fastness of dyed Leather:-
- Grey scale test to ascertain the change of colour and staining
- Fastness to light the standard Xenon lamp test
- Fastness towards mild washing
- Fastness towards washing by machine
- Colour Fastness with regard to migration into plasticized Poly Vinyl
Chloride
- Fastness towards perspiration
- Fastness to test of rubbing
- Fastness in water
- Fastness with respect to water spotting
- Solubility capacity of powder dyes
- Stabilty of dyes with regard to:
Criterias for determining the Colour Fastness of Dyed Leather 