Merceriser

Merceriser refers to an apparatus used to perform mercerization, a chemical treatment of cellulose fibers, primarily cotton, with sodium hydroxide (caustic soda). The process, named after John Mercer who first described it in the 1840s, improves dye uptake, strength, luster, and dimensional stability of the fiber.

In batch mercerising, fabric is wound or laid in a tank and immersed in a caustic liquor under tension. In continuous mercerising, fabric moves through a sequence of contact zones where liquor flow and tension are controlled. Typical concentrations of NaOH range from about 12% to 25%, with temperatures from ambient to warm (approximately 20–60°C). Contact times vary from a few minutes up to about an hour, depending on fiber type and desired effect. After treatment, the material is neutralized with a dilute acid bath (such as acetic or sulfuric acid), thoroughly washed, and dried.

The chemical action causes swelling and reorganization of the cellulose, often transforming part of the crystalline structure from cellulose I to cellulose II. This results in brighter and more uniform dye uptake, increased sheen, and improved dimensional stability. Tensile strength may rise modestly when mercerization is well controlled; excessive alkali or overexposure can weaken fibers.

Equipment and safety considerations include corrosion-resistant construction (glass-lined or stainless steel vessels and fittings) and proper handling of caustic solutions. Effluent treatment and protective equipment are essential due to the caustic nature of the process. Mercerisers are used in textile mills for cotton and other cellulose fibers, in both batch and continuous configurations.