Cotton yarns and fabrics can be given a lustrous sheen by altering the cross-sectional shape of the cotton fibres. This is done by soaking the yarns (or fabrics) in caustic soda and then neutralizing them in acid. The fibres become swollen making them much more cylindrical which gives them their characteristic lustre. Mercerized cotton as it is known is also stronger and has an increased affinity for dyes.
Lustrous, smooth-surfaced fabrics such as satins show wrinkles more easily than fabrics with rougher surfaces such as flannels. Filament yarns are frequently textured to improve properties. Texturing processes can introduce crimps, coils, snarls and crinkles into the filaments. Most processes use heat to set the yarn into the required profile. A process which does not require heat is air-jet texturing where loops are formed by over-feeding the filament into a turbulent air stream