Standard Salt Dosing Schedules for Reactive Dyeing Heavy Cotton Canvas
Progressive exponential salt dosing prevents surface strike spikes and forces reactive dye penetration into heavy cotton duck yarn cores.
Calcium Hardness
Water Quality
Dissolved multivalent alkaline earth cations, specifically calcium ions, represent a critical water contamination metric in commercial textile wet processing facilities. High calcium hardness causes precipitation of anionic dyestuffs, decomposes scouring detergents and generates insoluble soap curd on fabric surfaces. Mill intake water standardizes these concentrations as calcium carbonate equivalents measured in parts per million or French degrees.
Calcium cations coordinate with reactive and direct dye molecules, promoting premature dye agglomeration before complete migration occurs across the substrate.
Processing Consequence
Bleaching baths containing elevated calcium concentrations suffer from accelerated hydrogen peroxide decomposition when stabilizing silicate compounds aggregate. Residual calcium on cotton yarns increases yarn-to-metal friction coefficients during high-speed knitting, leading to yarn breaks and needle wear. Dyebath recipes require organic polycarboxylic or phosphonate sequestering agents to chelate free calcium ions into stable water-soluble complexes.
Analytical Method
Laboratory verification employs ethylenediaminetetraacetic acid titrations under alkaline conditions using eriochrome black T as an indicator. Standard titrimetric methods detect calcium hardness concentrations down to one part per million, alerting technicians when softening resins require regeneration.
Commercial Parameter
Water processing boundaries require total hardness levels below fifty parts per million for reactive dyeing and below twenty parts per million for delicate pastels. Reclaimed dyehouse water requires continuous softening and filtration before reintroduction into preparation ranges.