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Mordant dyes are a specialized class of colorants that require the presence of a mordant - a metallic salt or complexing agent - to achieve effective fixation on textile fibers. They do not interact directly with textile fibers as direct or reactive dyes do but work by creating stable coordination complexes called "lakes." The formation of these lakes occurs when a dye molecule attaches to a metal ion, which subsequently binds to the fiber substrate. This process yields a water-insoluble compound with excellent wash and light fastness properties.

The dye's molecular interaction usually involves hydroxyl, carboxyl, carbonyl and azo functional groups acting as ligands. Metal ions such as aluminum (Al3+), chromium (Cr3+), iron (Fe2+/Fe3+), copper (Cu2+), and tin (Sn2+) become coordinated by these ligands. For example, alizarin, a naturally derived anthraquinone dye, forms a deep red lake when combined with aluminum ions, showcasing enhanced chromatic stability and fiber affinity. This chelation mechanism not only fortifies the dye-fiber interaction but also modulates the final hue depending on the metal used - a phenomenon known as polygenicity.

Alfa Chemistry offers a broad portfolio of high-performance mordant dyes for both traditional and modern applications.