Electrolyte Dosing Schedules for Low Liquor Ratio Canvas Dyeing
Controlled progressive electrolyte dosing prevents rapid surface strike and core starvation when reactive dyeing dense cotton duck at low liquor ratios.
Linear Salt Feed
Dyeing Dosing
Controlled introduction of electrolyte solutions into reactive dye baths at a steady, mathematically constant rate optimizes exhaustion and prevents unlevel coloration. A linear salt feed delivers sodium chloride or sodium sulfate into the circulating liquor at a flat volumetric pace across a designated dosing period. By avoiding sudden concentration spikes, this chemical delivery method minimizes localized electrostatic shock between anionic dyes and cellulosic fibres.
Uniform electrolyte accumulation ensures steady dye migration into cotton or viscose matrices. Modern industrial dyeing machines use automated metering pumps to maintain this steady flow. Controlled delivery yields superior color uniformity across bulk fabric lots.
Migration Physics
Cellulosic fibres submerged in neutral aqueous baths develop negative electrical charges on their exterior surfaces, repelling anionic reactive dye molecules. Dissolved electrolytes provide positive sodium ions that shield this negative charge, allowing dyes to leave the liquor and adsorb onto cotton surfaces. A sudden influx of salt causes dyes to exhaust rapidly on accessible outer yarn layers, producing shaded selvedges and patchy coloration.
Feeding electrolyte linearly moderates this chemical shift, maintaining uniform dye distribution across the liquor. Molecules migrate deeply into twisted yarn cores before chemical fixation takes place. The resulting penetration produces even depths of shade throughout thick textile substrates.
Automated Dosing
Microprocessor-controlled dosing pumps pull concentrated brine solutions from dedicated chemical preparation tanks and inject them into the main machine loop. Unlike progressive dosing systems that begin slowly and accelerate exponentially, a linear process delivers an identical volume during every single minute of the dosing cycle. Circulation pumps sweep the injected brine through heat exchangers and across the fabric rope or yarn package within seconds.
Dosing runs typically span thirty to sixty minutes depending on fabric weight and dye class affinity. Sensors monitor electrical conductivity to confirm steady electrolyte expansion throughout the cycle. Bath parameters remain strictly controlled without relying on manual chemical additions.
Process Limitation
While a linear profile functions reliably for low-affinity reactive dyes, high-strike dyestuffs can exhaust unevenly during initial stages. Highly reactive dyes with rapid substantivity often require progressive dosing curves that supply trace quantities at first before increasing volume later. Utilizing a flat feed for high-affinity formulas can saturate outer yarn surfaces before interior fibres absorb adequate dyestuff.
Technicians evaluate liquor ratios, fabric construction and dyestuff exhaustion rates when selecting delivery profiles. Denser woven goods like heavy cotton twills demand longer dosing times to ensure uniform liquor flow. Chemical formulation and pump calibration must align to prevent expensive batch re-dyeing.