Mordant dyes

Many of the natural dyes are mordant dyes; Alizarine red (CI Mordant Red 8), Persian berry yellow (CI Natural Yellow 13) and Logwood black (CI Natural Black 3), for example, were of enormous importance in early textile printing.

Mordant dyes

Synthetic mordant dyes, sometimes described as chrome colours, have also been used in large quantities for printing cotton. The dyes themselves have little affinity for the fibre, but can be printed with additions of hydrolysable metal salts (mordants) to give dye–metal complexes during steaming. With some dyes the use of salts of chromium, aluminium or iron or, less frequently, nickel, cobalt or zinc gives different colours.

Good fastness properties and low dye costs are characteristic. These dyes are no longer of great importance, however, because of the problems they present under modern conditions. Their disadvantages include limited print paste stability (due to premature complexing), steaming times of up to 1 h and deterioration in fabric handle as a result of interaction between thickener and metal salt.