Colour Fastness of Printed and Discharge-Dyed Textiles

Printed textile colour fastness testing applies standard ISO 105 methods to printed fabrics while addressing unique challenges of print durability — pigment print binder film integrity under washing and abrasion, reactive print wash-off adequacy, digital inkjet print lightfastness, and discharge print colour accuracy after bleaching. Pigment printing (50–60% of global printed fabric by volume): dye-free pigment particles bound to fabric surface by acrylic or polyurethane resin binder (cured at 150–170°C) — fastness dominated by binder adhesion and film integrity rather than dye-fibre chemistry: washing fastness grade 3–4 (good), rubbing dry grade 4–5, wet grade 3–4, light fastness grade 5–7 (excellent for inorganic pigments, 4–6 for organic). Reactive print (screen or rotary, conventional textile printing): fastness equivalent to exhaust reactive dyeing if wash-off thorough — inadequate steaming (underfixation) or washing reduces all fastness grades by 1–2 units. Digital inkjet print fastness: acid ink on silk (grade 3–4 washing, 4–5 light); reactive ink on cotton (grade 3–4 washing, 4–5 light after steam fixation); disperse sublimation ink on polyester (grade 4–5 washing, 5–6 light — best digital print fastness). Discharge print fastness: ground dye (dischargeable reactive or vat dye) bleached by reductive discharge agent (sodium hydrosulfite, rongalite) — paste dye in discharge area (illuminant colour) — fastness of discharge print complex: ground remaining in non-discharge areas must be washfast, discharge agent must not degrade fibre, illuminant colour dye must resist discharge conditions. Discharge fastness test: wash test ISO 105-C06 condition matching care label, assess both discharge area and ground area colour change — discharge area colour shift if illuminant dye affected by residual reducing agent.