Mordant

A mordant or dye fixative is a substance used to set (i.e., bind) <a href="/facts/Dye/a1NSlcsG">dyes</a> on fabrics. It does this by forming a <a href="/facts/Coordination_complex/1tCyeQUm">coordination complex</a> with the dye, which then attaches to the fabric (or tissue). It may be used for dyeing fabrics or for intensifying <a href="/facts/Stain/7VhlycN8">stains</a> in <a href="/facts/Biological_specimen/u51y6uvM">cell or tissue preparations</a>. Although mordants are still used, especially by small batch dyers, they have been largely displaced in industry by <a href="/facts/Substantive_dye/vNQoboEG">substantive dyes</a>.
The term mordant comes from the Latin mordere, "to bite". In the past, it was thought that a mordant helped the dye "bite" onto the fiber so that it would hold fast during washing. A mordant is often a <a href="/facts/Polyvalency_(chemistry)/aQW0V4VH">polyvalent</a> <a href="/facts/Metal/PT8hNX6R">metal</a> <a href="/facts/Ion/3bePpDna">ion</a>, and one example is <a href="/facts/Chromium/6sVk6Uu7">chromium</a> (III). The resulting coordination complex of dye and ion is <a href="/facts/Colloidal/9EVucqND">colloidal</a> and can be either <a href="/facts/Acid/FySU18n1">acidic</a> or <a href="/facts/Base_(chemistry)/M9wA7qeM">alkaline</a>.

Mordant open-in-new

Mordant