Mercerisieren

Mercerisieren is a textile finishing process in which cellulose fibers, especially cotton, are treated with a caustic soda solution to improve luster, dye uptake, strength, and dimensional stability. Mercerized cotton typically dyes more evenly and yields brighter colors and a smoother appearance.

In general, the fabric is treated under tension with a concentrated sodium hydroxide solution (about 20–26%). The alkali penetrates the fiber, causing it to swell and undergo a structural change from cellulose I to cellulose II. The fabric must remain stretched during treatment to preserve the desired shape. After sufficient dwell time, the material is thoroughly washed to remove alkali and then neutralized with mild acid, rinsed again, and dried. Some systems use higher temperatures or different concentrations to intensify the effect, while modern processes optimize conditions to balance luster, dye uptake, and fiber strength.

Mercerisation yields several practical benefits. It increases luster and improves dye uptake for many dyes, particularly reactive and direct dyes, producing brighter, more uniform colors. It can also enhance tensile strength and dimensional stability and may alter the fabric hand to a crisper feel. However, improper conditions can damage fibers, cause yellowing, or reduce softness. The process also involves safety and environmental considerations due to the use of caustic soda and the need for effluent treatment.

Mercerisation was developed in 1844 by John Mercer and soon became a standard cotton finishing step. It is widely applied to cotton fabrics and blends where enhanced dye performance and a brighter appearance are valued, including fashion textiles, denim preparation, and home textiles.