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.
Soda Ash Dosing
Alkaline Control
Controlled introduction of dissolved sodium carbonate into textile dyebaths raises bath alkalinity to trigger covalent fixation reactions between reactive dyes and cellulose fibres. Precise soda ash dosing converts neutral exhaust baths into alkaline reaction environments with operating pH values between 10.8 and 11.2. The chemical increases the concentration of cellulosate anions along cotton polymer chains, driving nucleophilic addition or substitution with reactive dye groups.
Rapid or unmetered additions cause flash fixation, producing severe visual unlevelness, spot defects and ruined fabric lots.
Automation Technique
Modern dyeing machines employ progressive dosing curves that inject soda ash solutions across forty-five minutes using logarithmic or linear pump profiles. Linear ramps add constant chemical volumes per minute, whereas progressive profiles introduce small initial volumes before gradually increasing dosing rates as bath equilibrium establishes.
Quality Verification
Automated pH probes monitor machine circulation pipes to confirm smooth alkaline rise without sharp pH spikes. Post-fixation rinse water must undergo acid neutralization using acetic or citric acid until core fabric pH reaches neutral seven.
Chemical Boundary
Sodium carbonate dosing applies specifically to warm-exhaust reactive dye systems operating between fifty and sixty degrees Celsius. High-reactivity cold dyes or low-reactivity hot dyes require alternate bases, such as sodium bicarbonate or caustic soda mixtures, to achieve targeted fixation kinetics.