(1) Oil-drop dye stains: mostly on E/R blended fabrics; after dyeing there are oil-drop spots slightly deeper than the normal shade. Under a magnifying glass, the pile tips on the deep-shade parts show tiny beads and more pile than normal areas.

Cause: uneven singeing. On the deep parts, the pile was not singed away fully and formed fused tips at the ends, which absorb more dye, so the shade is deeper.

(2) Penetration defects: after dyeing, the fabric surface shows light and deep cloud-like patches.

Causes: 1) desizing and scouring are insufficient, or wax removed in processing re-attaches to the fabric; 2) in exhaust dyeing the liquor ratio is too small or the heating rate too fast, so the dye liquor becomes gel-like.

(3) Bleached holes: the greige fabric is normal, but after hydrogen peroxide bleaching there are broken warp or weft yarns forming small holes.

Causes: rust on the fabric surface, or iron ions in the bleaching water, reacting with hydrogen peroxide during bleaching and decomposing it locally.

(4) Other common defects: creases, alkali spots, yellow spots, wax streaks, singeing creases and conveyor marks. Most come from unstable pretreatment, uneven tension or temperature fluctuation.

Prevention: control singeing evenly, ensure complete desizing and scouring, remove metal ions from the water, control bleaching time and temperature, and keep pretreatment stable.