Visual Assessment
Uneven dye penetration creates distinct colour rings around cross sections of staple fibres in yarn packages. Ring dyeing defects occur when dyestuffs fail to reach the core during high speed package processing. Core unlevelness lowers fastness ratings during subsequent laundering cycles.
Visual assessment under standard daylight cabinets confirms the deficiency before bulk yarn reaches the knitting floor.
Penetration Depth
Liquor flow rates dictate dye molecule migration into dense wound packages. High pump pressures force liquor past exterior perimeters too rapidly for uniform internal diffusion. Rapid exhaustion kinetics trap colour on outer filaments while leaving inner regions completely white.
Laboratory cross section microscopy measures radial penetration percentages from sheath to core.
Fastness Loss
Unpenetrated fibre cores expose raw substrate when garments undergo abrasion or repeated washing. Crocking test results drop significantly because surface dye rubs off easily from poorly bonded areas. Colour fastness to light decreases when dye distribution lacks uniformity across the entire cross sectional area.
Consumer claims multiply rapidly if retail apparel fades unevenly during early service life.
Process Control
Liquor circulation reversals and retarding agents regulate dye uptake speeds inside commercial dyeing machines. Temperature gradient ramps prevent premature exhaustion onto exterior yarn layers before internal liquor reaches equilibrium. Automated dosing systems maintain strict chemical concentrations throughout the entire fixation cycle.
Finished lots undergo random coring tests to verify complete radial colour absorption prior to downstream fabrication.
