Colour, Decoration & Finishes

Applying Colour: Dyeing

Colour can be applied to textiles at several stages of production: to the raw fibre before spinning (called stock dyeing), to the spun yarn before weaving or knitting (yarn dyeing, which allows multicoloured woven patterns), or to the finished fabric (piece dyeing, the most common industrial method). The dye must form a chemical or physical bond with the fibre for the colour to be permanent. Different fibre types require different classes of dye: reactive dyes bond chemically with cellulose fibres (cotton, linen); acid dyes are used for protein fibres (wool, silk); disperse dyes are used for polyester and acetate, which must be dyed under high temperature and pressure because the dye molecules have to physically enter the fibre.

Resist dyeing techniques create patterns by preventing dye from reaching certain areas. Batik uses hot wax applied to fabric to resist the dye; where the wax is, the original colour is preserved. After dyeing, the wax is removed (by boiling or scraping), revealing the undyed pattern. Batik originated in Java and is used to create distinctive crackle-effect patterns in fashion and furnishing fabrics. Tie-dye creates patterns by tying or folding the fabric tightly before immersing it in dye; the bound areas resist penetration.

Printing Methods

Printing applies colour in a controlled pattern to the surface of a fabric, rather than immersing the whole cloth in dye. The most commercially important methods are:

• Block printing — the oldest textile printing technique. A carved wooden or lino block is coated with dye paste and pressed firmly onto the fabric. Each colour requires a separate block, and the process is slow and labour-intensive, giving each print a handmade quality. Block printing is used for craft production and high-end artisan fabrics but is impractical for mass production.
• Screen printing (flat bed and rotary) — a fine mesh screen stretched over a frame is coated with a light-sensitive emulsion. A photographic positive of the design is laid on the screen and exposed to UV light; where the light falls, the emulsion hardens. Where the design blocks light, the emulsion washes away, leaving open mesh. Dye paste is forced through the open mesh onto the fabric. One screen is made per colour. Flat-bed screen printing is used for shorter runs; rotary screen printing (cylindrical screens rotating around the moving fabric) is used for very high-volume production.
• Digital (inkjet) printing — a digital image file is printed directly onto treated fabric using modified inkjet heads that deposit reactive or pigment inks. There is no minimum print run, so individual bespoke designs or short runs are economical. Digital printing can reproduce photographic-quality images with unlimited colours in one pass. It produces less dye waste than screen printing but is slower and more expensive per metre for very large runs.
• Sublimation printing — a specialised digital printing method used specifically for white polyester fabrics. The design is first printed onto transfer paper using sublimation inks. The paper is then pressed onto the polyester fabric under high heat (~200 °C): the ink sublimes (converts directly from solid to gas) and the gas molecules diffuse into the polyester fibre, where they re-solidify permanently. The result is a vibrant, wash-resistant print with no hand feel (no ink layer on the surface). Used extensively for sportswear, cycling kit and soft signage.

Surface Decoration

Beyond printing, textiles can be decorated using added materials and stitching:

• Embroidery — decorative stitching worked onto a base fabric using a needle and thread. Traditional hand embroidery is very slow and is reserved for bespoke and couture work. Industrial machine embroidery uses computerised multi-head embroidery machines that simultaneously stitch the same design on dozens of garments; used for logos on workwear, caps and school uniform. The design is created as a digitised stitch file.
• Appliqué — pieces of fabric are cut out and stitched onto a base fabric to create a layered, dimensional design. The applied fabric can be plain, printed or itself embroidered. Appliqué is used in quilting, children's clothing and soft furnishings. Industrial versions use bonded appliqué (iron-on adhesive backing) for speed.
• Quilting — two or more layers of fabric are stitched together, usually with a layer of wadding (padding) in between, through a grid or decorative pattern of stitching. The stitching compresses the layers in a pattern, creating a textured, three-dimensional surface. Quilting provides warmth (the wadding traps air) and is used in bedding, padded jackets and upholstery.

Finishes and Treatments

After construction (or after dyeing), fabrics are frequently given a finish to improve their functional or aesthetic properties. Key finishes include:

• Waterproofing / Durable Water Repellent (DWR) — a chemical coating applied to the fabric surface causes water droplets to bead up and roll off rather than soaking in. Common on outdoor jackets, tents and umbrellas. DWR coatings wear off with use and washing and must be reapplied.
• Flame-retardant finish — a chemical treatment that reduces the flammability of the fabric by releasing non-combustible gases or forming a char layer when the fabric is exposed to flame. Legally required for children's nightwear (the Nightwear (Safety) Regulations 1985), upholstered furniture and contract (public building) soft furnishings.
• Stain-resistant finish — a fluorocarbon or silicone coating reduces the surface energy of the fibres, causing liquids to bead on the surface before they can be absorbed. Used on school ties, table linen and upholstery. The finish makes the fabric easier to clean but must be reapplied periodically.
• Crease-resistant (easy care) finish — a resin applied to cotton or linen fabrics cross-links the cellulose fibres at the molecular level, preventing the hydrogen bonds that cause creasing from forming when the fabric is wet or worn. This makes the fabric easier to iron and helps garments retain their pressed shape. A trade-off is slightly reduced strength and absorbency.
• Brushing (raising) — a mechanical finish in which the fabric surface is passed over rollers covered with fine wire hooks that lift fibres into a soft nap. Brushed cotton (flannelette) and fleece fabrics are examples; brushing improves warmth by trapping more air in the raised surface.

Smart and Technical Textiles

Smart textiles respond to changes in the environment and can actively adapt their properties. Technical textiles are engineered for high-performance applications rather than appearance:

• Gore-Tex — a laminated membrane bonded to an outer fabric. The membrane contains over 1.4 billion microscopic pores per square centimetre: large enough to let water vapour (sweat) pass outwards but too small to let liquid water droplets in from the outside. This gives Gore-Tex its waterproof-yet-breathable properties. Used in hiking jackets, ski wear and surgical gowns.
• Conductive (e-textiles) — yarns incorporating metal-coated fibres or fine stainless steel threads can carry electrical current, allowing electronic components such as sensors, LEDs or heating elements to be integrated directly into a garment. Applications include heated motorcycle gloves, ECG monitoring shirts and wearable fitness trackers.
• Thermochromic textiles — thermochromic textiles contain pigments (usually microencapsulated leuco dyes) that change colour at a specific temperature. Applications include novelty T-shirts, swimwear that changes colour in warm water, and neonatal medical garments where a colour change signals that a baby's temperature has dropped below a safe threshold.
• Phase-change materials (PCMs) — microcapsules of wax embedded in fibre or applied to fabric absorb heat as they melt (during activity, slowing overheating) and release heat as they re-solidify (during rest, slowing cooling). PCMs are used in high-performance base layers for mountaineering and military applications.