Introduction
Emphasis on fault prevention and elimination of re-dyeingnot only brings substantial water and energy savings but also results in higherquality, increased productivity, reduced labour costs and advantages insupplier-customer partnership. Ferrington1 and Glover et al2have discussed and calculated the impact of re-dyeing cost. Considerable workhas been carried out to optimize and ensure maximum reproducibility in dyeing.Reviews on this subject have been published3. The quality of water,grey preparation, dyeability of the substrate, weight of the substrate,weighing of dyes and chemicals, selection of dyes, standardization of dyestrength (hue), moisture content of dyes and substrate, nature of dye bath,machine flow and sequence, time and temperature profile are the factors whichare responsible for the complexity of dyeing processes. One of these factors,i.e. moisture content of the dye powder is recognized as being influential fordepth of shade and reproducibility; however only a few quantitative resultshave been published on its effect and its consequences on dyeing. Adamiake4reported the effect of variations in moisture content of wool dye powder ondepth of the shade. One reason for variation in moisture content of dye powderis improper storage condition in dyeing factories. Many dyeing factories do notpay attention in storing dyes and chemicals. The stores personnel afterissuing dyes and chemicals to production department do not bother to close thecontainers properly. Therefore these dyes and chemicals get exposed to varyingtemperatures and humidity depending upon the seasons. The change in humidityresults in change in weight of the dye powder. The present work is an attemptto quantify the change in depth of shade due to change in humidity.
Even though reactive dyes have excellent wash fastnessproperties, often buyers complain of poor wash fastness. This is mainly due toadherence of hydrolysed dyes onto cotton. If they are not washed off afterdyeing, they behave like direct dyes and bleed during the initial washingscarried out by the customers. In order to avoid the complaints, some dyers takeextra precautions by providing more than the required number of washings.Therefore the second objective of the present study is to develop a quickmethod to optimize the number of washings to be given after reactive dyeing toachieve good wash fastness properties, especially for dark and medium shades.
About the Authors
The authorsare associated with Northern India Textile Research Association, U.P, and GinniDevi Modi Girls (P.G) College, Modinagar.
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