An analysis of the factors influencing unlevelness of a direct dye on a pilot-scale jet dyeing machine

The investigation used a pilot-scale jet dyeing machine to examine the relationship between the dye exhaustion rate per contact and dye unlevelness on the fabric. It was found that a commercially acceptable degree of unlevelness could be obtained for a direct dye on pure cotton fabric as long as the exhaustion rate did not exceed 1.0% per contact, independent of the dye amount used. Bath contacts and fabric contacts influenced unlevelness in equal manner. Non-ionic surfactants, which had been selected so as not to influence the dye exhaustion rate or its equilibrium uptake, appeared to have little or no influence on unlevelness. Control of the dye uptake by electrolyte addition proved to be a more efficient dyeing strategy than controlling it by dye addition, as unlevelness in the first case was much lower at the same exhaustion rate.