A mordant is a substance used to set dyes on fabrics or tissue sections by forming a coordination complex with the dye which then attaches to the fabric or tissue. It may be used for dyeing fabrics, or for intensifying stains in cell or tissue preparations. A mordant is always a polyvalent metal ion. The resulting coordination complex of dye and ion is colloidal and can be either acidic or alkaline. Common dye mordants Mordants include tannic acid, alum, urine, chrome alum, sodium chloride, and… (More on Mordant)