Fabric finishes, colouration and textile properties
Why finishes matter
Finishes change performance, handle or appearance and should be specified on the design brief. Preparatory treatments include desizing, scouring and bleaching; mercerising cotton in caustic soda under tension increases lustre, strength and dye uptake. Mechanical finishes include calendering, sanforising (cotton shrinkage held below about 1%), raising, peaching and embossing; heat setting stabilises polyester. Chemical finishes include easy-care/durable-press resins on cellulose (fewer creases but lower strength and absorbency), softeners, water-repellent and stain-repellent finishes, flame retardants and antimicrobials.
Colouration
Dye choice follows fibre chemistry: reactive dyes bond covalently to cotton and give good wash fastness; vat dyes such as indigo suit denim; acid dyes suit wool, silk and nylon; disperse dyes are needed for polyester; basic dyes suit acrylic. Dyeing can happen at fibre, yarn, piece or garment stage - earlier stages give more even colour, later stages allow quick response. Printing methods include flat and rotary screen, digital, block and transfer; discharge and resist create pattern by removing or blocking dye.
Testing properties
Fastness is judged by wash, light (blue wool scale 1–8, 8 best), rubbing wet and dry, and perspiration, against grey scales. Other tests cover absorbency, tenacity, elastic recovery, crease recovery, pilling and abrasion.
Worked example: a cotton T-shirt that must survive repeated hot washing should be dyed with reactive dyes, not pigment, because the covalent bond remains after washing, whereas pigment sits on the surface held by binder and crocks.
Traps: confusing water-repellent with waterproof; forgetting easy-care reduces absorbency; thinking mercerising is a dye; assuming a high blue wool number means poor light fastness.