mordanti

Mordanti are chemical compounds used primarily in textile dyeing and printing to improve the adhesion of dyes to fabrics, particularly natural fibers such as cotton, wool, silk, and linen. The term originates from the Latin *mordere*, meaning "to bite," reflecting their role in "binding" dyes to fibers. Without mordants, dyes may wash out or fade quickly, reducing the longevity and vibrancy of the colored fabric.

Common mordants include metallic salts such as aluminum potassium sulfate (alum), iron sulfate, chromium sulfate, and tin chloride. Organic mordants, like tannins derived from plant sources, are also used, particularly in traditional dyeing techniques. Mordants work by forming coordination complexes with dye molecules, creating a chemical bond with the fiber’s surface. This process enhances colorfastness, ensuring dyes remain stable under exposure to light, water, or friction.

In historical and artisanal dyeing, mordants were essential for achieving consistent and durable results. For example, alum was widely used in medieval Europe to fix wool and silk dyes, while copper sulfate was employed for cotton. Modern synthetic dyes often require mordants to achieve optimal adhesion, though some modern fabrics, particularly synthetics, may not need them due to their inherent dye-affinity properties.

Mordants are also applied in other fields, such as leather tanning, where they help fix dyes to animal hides, and in microscopy, where they enhance the visibility of stained biological samples. The choice of mordant depends on the fiber type, dye used, and desired color outcome, with different combinations producing varying shades and fastness levels. Proper application techniques, including pre-mordanting fibers and controlling pH levels, are critical to achieving successful results.