Dye Definitions — definitions of dyes, pigments and dyeing terms from Apparel Search
A mordant is a substance used to set dyes. A mordant is either inherently colloidal or produces colloids, and can be either acidic or basic. Mordants include tannic acid, alum, chrome alum, and certain salts of aluminum, chromium, copper, iron, potassium and tin — the agents that let natural dyes such as madder, weld and cochineal hold fast to fiber instead of rinsing away.
A mordant is a substance used to set dyes. A mordant is either inherently collodial or produces colloids and can be either acidic or basic.
Mordants include tannic acid, alum, chrome alum, and certain salts of aluminum, chromium, copper, iron, potassium, and tin.
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| The above article is licensed under the GNU Free Documentation License. From Wikipedia, the free encyclopedia (https://en.wikipedia.org/wiki/mordant). Modified by Apparel Search 11/09/04 |
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How a Mordant WorksMost natural dye molecules have only weak attraction to textile fibers on their own. A mordant solves the problem in two steps: the mordant is applied to the fiber first (or added to the dyebath), where its metal ions attach to the fiber, and the dye then attaches to the metal, forming an insoluble colored complex locked on the fiber. That single mechanism explains both sides of mordanting — the wash fastness that makes a natural dye practical, and the shade shifts that dyers exploit deliberately. Madder on alum gives the famous Turkey red family of reds; the same madder with iron turns toward purple-brown. Logwood with iron gives deep black, historically the standard black for wool and silk. A dyer's mordant notebook is therefore a color library, not just a fixing recipe. Mordanting in PracticeWool and silk, being protein fibers, take up metal mordants readily; cotton and other cellulose fibers resist them, which is why cotton mordanting classically begins with tannic acid, giving the fiber a coating the metal salt can then grip — the tannin-and-alum sequence behind generations of printed and dyed cottons. Timing is flexible: fiber can be pre-mordanted before dyeing, mordanted and dyed in one bath, or treated after dyeing to shift or fix the shade. Chrome mordants give excellent fastness and were industrial standards for wool, but chromium's environmental cost has pushed modern practice toward alum and iron, the two mordants today's natural-dye revival is built on. In every era the principle is unchanged: the mordant is not the color, but without it the color does not stay. Mordants Beyond Natural DyesThe word also survives in industrial dyeing, where mordant dye classes — dyes applied with a chrome mordant for maximum fastness on wool — took their name from the process. Even where synthetic dyes have replaced natural ones, the underlying idea, preparing the fiber so color can bond, remains the first step of coloration chemistry. Common QuestionsWhat does a mordant do in dyeing?A mordant sets dye on fiber. It forms a bridge between the dye and the fiber so the color bonds durably instead of washing out, which is why most natural dyes cannot be used successfully without one. Which substances are used as mordants?Tannic acid, alum and chrome alum, and certain salts of aluminum, chromium, copper, iron, potassium and tin. Each is either inherently colloidal or produces colloids, and a mordant can be either acidic or basic. Does the choice of mordant change the color?Yes. The metal in the mordant becomes part of the final color complex, so the same dye gives different shades with different mordants — alum keeps colors bright, while iron darkens or saddens them toward grey, brown and black. More to ExploreMore from Apparel Search: Dye Definitions | Clothing Industry Glossary | Fashion Terms | Apparel Search Home
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