Guide des techniques de finissage textile

Mercerization involves immersing cotton under tension in a caustic soda solution (NaOH 18-25%) at low temperature (15-20°C). This operation causes the irreversible swelling of cellulose fibers, transforming their irregular cross-section into a circular one. The result: a permanent silky lustre (+20-25% light reflection), a 20-25% increase in tensile strength, better dye affinity (+30% dye absorption) and improved dimensional stability. The process is permanent and does not fade with washing. Maisons such as Hermès, Loro Piana and Misciano systematically use mercerized cotton for their shirts and premium cotton linings.

Calendering passes the fabric between heated metal rollers (80-200°C) under pressure (50-300 kN/m). The flattening of the fibers creates a smooth, shiny surface. Variants: Schreiner calendering (engraved at 200 lines/cm for a satin lustre), friction calendering (one roller rotates faster for a glazed effect), embossing calendering (raised patterns). The effect is semi-permanent: it fades after 5-10 washes except on thermoformed synthetics. Very low cost, applicable to all fibers. Widely used for linings, sheets and upholstery fabrics.

Sanforization is a mechanical pre-shrinking process patented by Sanford Cluett in 1930. The moistened fabric passes over a compressible rubber sleeve that compresses it in the warp direction, reducing residual shrinkage to less than 1% (ISO 5077 standard, versus 5-8% without treatment). The process is purely mechanical (no chemicals), permanent, and affects neither the hand feel nor the color of the fabric. Essential for ready-to-wear: an unsanforized Levi's jean shrinks by 2-3 sizes on the first wash. All Misciano shirts are sanforized to guarantee perfect size stability.

Brushing (raising) uses rollers fitted with metal points or natural teasels (gig mill) to extract fibers from the fabric surface, creating a soft, insulating nap. Flannel, fleece, and peach-skin are obtained through brushing. The intensity of the treatment (number of passes, speed, type of covering) determines the thickness of the nap. Brushing increases thermal insulation by 30-50% but reduces abrasion resistance by 20-30%. Used for flannel sheets, winter coats, and thermal linings.

Singeing consists of passing the fabric quickly (60-200 m/min) over a gas flame or heated plate to burn off surface fibers (nap). The result: a clean, crisp surface, better dyeability (fewer loose fibers that pick up color unevenly), reduced pilling, and a smoother appearance. Singeing is systematically carried out before mercerization. Critical precaution: the fabric must be immediately quenched after singeing to extinguish any residual embers.

Bio-polishing uses cellulases (enzymes) to selectively digest protruding microfibrils on the surface of cotton fabric. The result: a smoother surface, a softer hand feel, permanent reduction of pilling, increased lustre and more vibrant colours. Unlike chemical treatment, bio-polishing is biodegradable, generates no toxic waste and operates at low temperature (40-55C, pH 4.5-5.5 for acid cellulases). Novozymes and DuPont are the main suppliers of textile enzymes. Enzymatic stone-washing (cellulases + pumice stones) replaces traditional stone-washing with 50% less water.

Coating consists of depositing a layer of polymer (PU, PVC, acrylic, silicone) onto one side of the fabric using a doctor blade, roller or spray. Applications: waterproofing (water column 5,000-20,000 mm), windproofing, tear resistance, synthetic leather appearance. Microporous PU coatings (breathable) offer an RET of 8-12, compared to an RET of 20+ for non-breathable PVC coatings. Fluorocarbon DWR (Durable Water Repellent) is gradually being replaced by fluorine-free alternatives (C0-DWR) compliant with REACH regulations. Coating reduces fabric breathability but considerably improves its resistance to water and wind.

Lamination bonds a waterproof and breathable membrane (expanded PTFE, PU, polyester) between the outer fabric and the lining, creating a high-performance multilayer textile. Gore-Tex (ePTFE membrane, 1.4 billion pores/cm2) achieves a water column of 28,000 mm with a Ret of 3-6 (highly breathable). The 2-layer, 2.5-layer, and 3-layer constructions offer different levels of protection and weight. Lamination is the most expensive technique but offers the best waterproofing-breathability performance. Sympatex (hydrophilic membrane without pores) and eVent (hydrophobic membrane with direct ventilation) are the main alternatives.

DWR (Durable Water Repellent) is a surface treatment that makes the fabric hydrophobic without clogging the pores (unlike coating). Fluorocarbon DWRs (C8, C6) offer the best performance (contact angle >150 degrees) but are progressively banned (PFAS, REACH regulation). Fluorine-free alternatives (C0-DWR) based on silicone, paraffin, or dendrimers achieve a contact angle of 120-140 degrees. Durability varies: 20-50 washes for a fluorocarbon DWR, 10-20 for a fluorine-free one. Reactivate by hot drying (20 min, 60C). Archroma Smartrepel, Rudolf Bionic-Finish Eco, and Huntsman Phobotex are the market references.

Flame retardant treatment gives the fabric fire resistance (self-extinguishing, no flame propagation). Proban (gaseous ammonia + THPOH) and Pyrovatex (phosphorus-nitrogen resin) treatments are the references for cotton, with durability of 50+ industrial washes. Halogen-free flame retardants (phosphorus, silicone, intumescents) are progressively replacing brominated formulations. Key standards: EN ISO 11612 (protective clothing), EN 13501 (construction materials), NFPA 701 (upholstery textiles). Flame retardant treatment modifies the hand feel (stiffer) and can reduce breathability by 10-20%.

Antimicrobial treatments inhibit the growth of bacteria, fungi, and mites on textiles. Active agents: ionic silver (Ag+), zinc pyrithione, chitosan, quaternary ammonium salts. Test standards: ISO 20743 (antibacterial activity), AATCC 100, JIS L 1902. Durability ranges from 20 to 100 washes depending on the technology. Nano-silver (Sanitized Silver) offers the best durability but raises environmental concerns (ecotoxicity). Bio-based alternatives (chitosan, microencapsulated essential oils) are growing. Applications: socks, underwear, sportswear, medical textiles.

Softening involves the application of lubricating agents (silicones, polyethylene, fatty acids) that reduce friction between fibers, giving the fabric a softer hand feel and better drape. Aminofunctional silicones (macro and micro emulsions) offer the silkiest touch and best drape but may yellow whites. Non-ionic softeners are more stable. Durability is limited: 5-15 washes for standard softening, 20-30 for reactive silicone treatments. Softening can reduce water absorption and dye affinity. Used on virtually all apparel and home textiles.

Heat-setting involves heating the synthetic fabric to a temperature above its glass transition temperature (Tg) but below its melting point, under controlled tension. Polyester: 180-210°C for 20-30 seconds. Nylon: 160-185°C. The operation fixes the fabric's dimensions, eliminates internal stresses, and stabilizes shape (permanent pleats, plissé). Residual shrinkage drops to less than 0.5%. Heat-setting is essential for synthetic fabrics and blends: without it, the fabric deforms during washing, ironing, and wear. Performed on a stenter frame with precise temperature and tension control.