There are many causes for white spots during dyeing, such as water spots from the dyeing padding‑off machine and the reduction steamer. Relatively bright white spots originate from an earlier process section, while faint mild spots are generated at a later section. Round‑shaped water spots are formed where fabric travel height difference is small or caused by liquid splashing. Elongated strip‑shaped water spots occur at positions with large height differences along the fabric transport path.
Some white spots are caused by woven bag fragments caught in the mercerizing padder, which lead to white spots upon dyeing. Cotton lint trapped in the mercerizing padder will result in dark spots after dyeing. Other sources of white‑spot defects include wax stains, alkali sludge and rotted‑cotton stains.
Fabric Quality Control
In production, good‑quality grey fabric delivers high dye uptake and good depth‑building performance, yielding a smooth, uniform and full fabric surface. Poor‑quality grey fabric tends to exhibit severe white specks and streaky defects after dyeing. For grey fabric with high content of dead cotton and cotton impurities, enhance the pre‑treatment process. While ensuring safe and stable production, remove cotton impurities as thoroughly as possible and fully boil out dead cotton to improve dye uptake and finished dyed‑fabric quality.
Cold‑pad batch pre‑treatment is widely adopted by many manufacturers for its energy‑saving benefits. Nevertheless, it shows limited performance in removing cotton impurities and size, and tends to render fabrics stiff. This causes creasing during dyeing, and dirt buildup on guide rollers which triggers dirty spots and color stains. Therefore, viscous auxiliaries such as anti‑migration agent and brightener NT‑2 shall be used sparingly in dyeing production.
Treatment for Polyester Brushed Fabrics and Heavy‑Weight 100% Cotton Fabrics
When producing polyester‑cotton brushed fabrics or heavy‑weight pure‑cotton fabrics, insufficient washing after bleaching leaves fine cotton lint adhering to the fabric surface. Compacted by padder pressure, such lint becomes extremely hard to remove and forms white spots in subsequent dyeing. Certain white spots are barely visible right after padding‑off, yet numerous white spots will appear once the lint falls off when rubbing the fabric surface against the grain. Some micro cotton lint sticks tenaciously to fabric and cannot be detected after continuous dyeing. White spots only emerge during stenter finishing when viscous auxiliaries including anti‑wrinkle agent, water‑repellent agent and cross‑linking agent peel off the adhered lint.
White spots induced by cotton lint should not be underestimated. For brushed‑fabric production, frequently clear cotton lint accumulated in the air duct, exhaust fan and brushing rollers of the brushing machine, to prevent lint from sticking onto fabric and being compacted by the delivery padder and becoming non‑washable. If cotton lint cannot be fully removed after two washing cycles, run the fabric through the brushing roller on the brushing machine one more time prior to dyeing for thorough lint elimination.
Remedial Treatment for Low‑Grade Fabrics
For fabrics rich in cotton impurities and dead cotton, increasing alkali concentration to 220 g/L during mercerization effectively improves dyed‑fabric surface quality and mitigates white specks and streaks.
Great attention must be paid to chafe marks in subsequent processes after brushing brushed fabrics. Chafe marks will turn into white spots after dyeing. Accordingly, padders and guide rollers shall be free of hard foreign objects during post‑brushing mercerizing alkali washing, with frequent patrol inspections. If chafe‑mark‑caused white spots are found before dyeing, carry out remediation before dyeing proceeds.
A practical case was encountered in two‑bath dyeing (disperse / reactive dyes) for polyester‑cotton brushed fabrics: white spots spotted in disperse dyeing were not taken seriously, and severe white‑spot defects were only noticed when over‑dyeing with reactive dyes, prompting belated remediation. To eliminate chafe marks on brushed fabrics, the brushing effect has to be compromised. Re‑mercerization with higher alkali concentration equalizes the nap feeling of unaffected areas and chafe‑mark zones, so that white spots originating from chafe‑marks become invisible.
Post time: Aug-19-2026