Mercerization is a treatment for cotton fabric and thread mostly employed to give cotton a lustrous appearance. The series of processes was devised by John Mercer in the middle of the 19th century.

Mercerized cotton is sometimes referred to in the crafts as pearl or pearle cotton. It is cotton yarn or fabric which has been put through a series of processes, primarily to increase luster. The added desirable water handling properties gained are a secondary bonus.

In 1851, John Mercer was granted a British Patent for work he had done pertaining to cotton, linen and other vegetable fibrous materials that in effect caused certain changes in the character of the fiber when subjected to caustic soda, sulfuric acid, and/or other chemicals, etc. He went on to list a number of these changes, one of which was that caustic soda caused the fiber to swell, become round and straighten out (but it did not impart any change in luster). At the time Mercer introduced these processes, the British cotton trade showed no interest in any of it and it all sat in obscurity for about forty years. In 1890 Horace Lowe was granted a British patent in which he claimed that by applying Mercer's caustic soda process to cotton yarn or fabric under tension a resultant high luster (a result of the light reflection off the smooth, round surface) was imparted to the fiber. It became an overnight success and revolutionized the cotton industry.

Mercerized cotton is cotton thread (or cotton-covered thread with a polyester core) that has been treated with sodium hydroxide (NaOH). The thread is given a caustic soda bath that is then neutralized with an acid bath. This treatment increases strength, luster, affinity to dye and resistance to mildew, and also reduces lint. Long staple fiber lengths respond best to mercerization.

Textiles | Merzerisation