Some dyes combine with metal salts (mordanting) to
form insoluble colored complexes (lakes). These materials are usually
used for the dyeing of cotton, wool, or other protein fiber. The fiber is
first treated with an aluminum, chromium, and iron salt and then
contacted with a lake-forming dye (azo and anthraquinone derivatives).
The metallic precipitate is formed in the fiber producing very
fast colors highly resistant to both light and washing.
