Mercerization

Mercerization is a chemical finishing treatment applied mainly to cotton and flax fabric or yarn, most often by soaking it in a 20 to 26 percent solution of sodium hydroxide before thoroughly washing it out, which increases the fiber's strength, improves how readily it takes up dye and reduces later shrinkage. The English scientist John Mercer created the treatment in 1844, and of the effects he observed he considered the improved dye uptake the most technically important, though he also experimented separately with sulfuric acid and zinc chloride, discovering what became known as the parchmentizing effect. The glossy, silk-like sheen now most associated with mercerized cotton was not part of Mercer's original process; Horace Lowe discovered in 1889 that holding the fabric under tension during the treatment, which straightens the fiber's cross-section toward circular, produces that characteristic luster.