Economic Aspects of the Dyeing of Cotton Knitgoods with Reactive Dyes in Winches and Jet Machines

Abstract

The choice between alternative dye recipes to match the same colour using reactive dyes on cotton does not reduce simply to comparing the costs of the individual dyes and their proportions in the recipes. Often the conditions of application of the recipes are significantly different and it is not sufficiently accurate to represent process cost by a constant factor independent of applied depth or dyeing‐cycle profile. For example, depending on the dyeing cycle and machine selected, a pale depth costing perhaps 5 pl kg for the dyes required would demand a further 10–25 p/kg in process costs, even if no shading problems arose. The processing ‘surcharge’ on a 50 p/kg full‐depth recipe would amount to 15–40 p/kg dyed faultlessly.The cost‐effectiveness of the process is adversely affected if shading and reprocessing become necessary. Shading corrections to a pastel dyeing may be almost negligible in terms of dye cost but an extra 10–15% in processing cost is registered each time. A substantial addition to a full‐depth dyeing from a fresh bath is a severe penalty, however, amounting to a major proportion of the cost of the original dyeing. The contribution of the fixed‐cost component to the total costs of dyeing can become a heavy burden if the productive capacity is not being effectively used. It makes no economic sense to replace an unsophisticated but still viable winch by a costly jet machine unless the available workload and technological control systems can justify this decision by ensuring that the new machine is kept full and effectively occupied throughout its productive life. The relationships between these factors are illustrated by means of typical examples, based as far as possible on realistic recipe costs and process details.