While talking about Dyes; many questions arise in reader's mind; like: What is exhaustion? What is a bi-functional dye? What are hot brand, medium brand and cold brand dyes? and many more...


These are explained in brief along with many other frequently asked questions in fabric dyeing:


What is an alternative production process?


Alternative, cleaner production techniques provide an effective way to examine an existing production system to pinpoint areas where changes could be made which will optimize the production process.


Thus it can help to realize the benefits of process optimization, quality control, energy conservation and preventive management. It can also lower energy and costs associated with:


  • raw materials
  • energy
  • labour
  • treatment and disposal
  • insurance and liability


This is an integral part of the environmental management system.


What are optimum recipes?


An optimum recipe is the recipe for which we need to use minimum dyes and chemicals but will achieve the correct shade first time with the maximum fixation. This will mean that there will be less wastage of dyes and chemicals and reduce the effluent load. This will also include optimizing the dyeing process.


How can we get optimum recipes?


Yes, optimum recipes can be achieved but require the evaluation, implementation and control and monitoring of various dyeing parameters; this will include, dye selection, measuring the exhaustion and fixation of dyes, monitoring dyeing temperatures, pH, liquor ratio and time. In addition to controlling the dyeing process, careful attention must be paid to the quality and storage of dyes and chemicals in order to avoid variation in materials between batches.


Careful monitoring of lab to bulk recipes needs to be undertaken together with establishing good communication between the lab and the plant.


Why is knowledge of dye chemistry important?


While selecting dyes it is sometimes difficult to select compatible dyes if little information is given by a dyestuff supplier. It is the utmost duty of dye manager or production manager to select the best dyes for his production. Various parameters to be considered including: dye cost, quality of dyes, dyeing process, and shade matching. There are various types of dyes for many textile fibres; for example, reactive dyes, vat dyes for cotton, acid dyes for wool, silk and polyamide fibres. Cotton reactive dyes such as vinyl sulphone or mono chloro triazine have a different reactive group which will require distinctive application conditions. A knowledgeable dyer will be able to recognize the reactive group on the dye molecule from its chemical structure and be able to specify the correct application conditions for the specific dye and be able to select compatible dyes for 3 dye combination shades.


What is exhaustion?


In exhaust dyeing, all the material contacts all the dye liquor and the fibre absorbs the dyes. The dye concentration in the bath therefore gradually decreases. The degree of dye bath exhaustion is therefore a function of time describes the rate and extent of the dyeing process. For a single dye, the exhaustion is defined as the mass of the dye taken up by the material divided by the total initial mass of dye in the bath.