Introduction
Emphasis on fault prevention and elimination of re-dyeing
not only brings substantial water and energy savings but also results in higher
quality, increased productivity, reduced labour costs and advantages in
supplier-customer partnership. Ferrington1 and Glover et al2
have discussed and calculated the impact of re-dyeing cost. Considerable work
has 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 dye
strength (hue), moisture content of dyes and substrate, nature of dye bath,
machine flow and sequence, time and temperature profile are the factors which
are responsible for the complexity of dyeing processes. One of these factors,
i.e. moisture content of the dye powder is recognized as being influential for
depth of shade and reproducibility; however only a few quantitative results
have been published on its effect and its consequences on dyeing. Adamiake4
reported the effect of variations in moisture content of wool dye powder on
depth of the shade. One reason for variation in moisture content of dye powder
is improper storage condition in dyeing factories. Many dyeing factories do not
pay attention in storing dyes and chemicals. The stores personnel after
issuing dyes and chemicals to production department do not bother to close the
containers properly. Therefore these dyes and chemicals get exposed to varying
temperatures and humidity depending upon the seasons. The change in humidity
results in change in weight of the dye powder. The present work is an attempt
to quantify the change in depth of shade due to change in humidity.
Even though reactive dyes have excellent wash fastness
properties, often buyers complain of poor wash fastness. This is mainly due to
adherence of hydrolysed dyes onto cotton. If they are not washed off after
dyeing, they behave like direct dyes and bleed during the initial washings
carried out by the customers. In order to avoid the complaints, some dyers take
extra precautions by providing more than the required number of washings.
Therefore the second objective of the present study is to develop a quick
method to optimize the number of washings to be given after reactive dyeing to
achieve good wash fastness properties, especially for dark and medium shades.
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About the Authors
The authors
are associated with Northern India Textile Research Association, U.P, and Ginni
Devi Modi Girls (P.G) College, Modinagar.