Calculated Cover Factor Metrics for Heavy Cotton Twills in Batch Dyeing
Heavy twill cover factors above twenty-two impede jet dyebath penetration, requiring lowered heating rates and increased anti-crease lubrication.
Reactive Dye Migration
Levelling Kinetics
Dye redistribution during wet processing refers to the movement of dye molecules from areas of high concentration to areas of lower concentration on a substrate. For cellulosic fibres, reactive dye migration occurs during the initial exhaustion phase before the addition of alkali triggers covalent bonding. This phase allows the dye to distribute evenly throughout the fabric structure, establishing a uniform base of color.
High migration efficiency is essential for preventing uneven dye distribution.
Thermal Influence
Salt concentrations and bath temperature govern the rate of dye movement before the fixation phase begins. In reactive dye migration, increasing the temperature enhances molecular mobility, allowing dyes to desorb and re-adsorb more freely. However, if alkali is added too early, the dye molecules fix permanently to the cellulose, ending the migration phase.
Processing mills must therefore separate the exhaustion and fixation steps carefully to achieve optimal leveling.
Process Control
Laboratory testing evaluates the migration properties of individual dye combinations to ensure compatibility in multi-shade recipes. To measure reactive dye migration, a piece of dyed fabric is treated in a blank bath alongside an undyed sample under production conditions. The amount of dye that transfers to the white fabric indicates the migration capacity of the dye.
Technicians use these results to select dyes with matching migration behavior for composite shades.
Quality Inspection
Production results show that poor migration leads to localized shade variation and costly stripping procedures. Ensuring adequate reactive dye migration reduces the need for correction and prevents streaking on finished garments. This control step is verified by checking shade consistency across the width of the fabric roll.