Liquor Absorption
The mass ratio of absorbed chemical solution to dry fabric substrate defines the wet pickup rate during continuous foulard padding operations. Standardized continuous padding pickup percentage calculations ensure exact chemical add-on rates across woven or knitted fabric lots passing through squeezed mangle rolls. Wet pickup determination compares dry fabric mass before padding against wet fabric mass immediately following mechanical expression.
Maintaining steady absorption values prevents shaded dye lot variations along length and width.
Squeeze Calibration
Pneumatic or hydraulic pressure applied across padding rolls determines the final volume of liquid retained within fabric pore spaces. Uniform nip pressure distribution prevents center-to-selvedge pickup variations that cause shading defects during thermal fixation. Differential roll hardness alters liquor extraction efficiency, requiring routine shore hardness verification of rubber roll covers.
High squeeze pressures reduce thermal energy requirements during subsequent drying stages by lowering total moisture content.
Migration Control
High wet pickup levels leave excess surface liquor free to migrate toward fabric surfaces during initial infrared drying, creating uneven color distribution. Lowering pickup values from eighty percent to fifty percent reduces dye migration while lowering natural gas consumption in intermediate dryers. Pick-up levels below critical saturation thresholds cause uneven wetting and streaky chemical deposition across dense woven structures.
Substrate Density
Dense cotton canvas fabrics require higher roll pressures to achieve target pickup values compared to open knit structures.
