whenever a textile material to be dyed at a desired shade(say 1% which means dyes to be added @ 1% OWM). but to assess to the dyeing effect it is followed by color coordinates(L*, a b Or L*, c, h) not by amount of dyes have been fixed or added to the textile materials(though i can understand: dye adding and its effect are two different things). or is it possible practically or theoretically to match the ultimate shade exactly before dyeing using color coordinates?
one more thing, say dyeing textile material at 1% shade @ 1:10(M:L) and at the same shade @ 1:7 and 1:15 and 1:20. the ultimate effect will not definitely be the same. So how is a fabric or any textile material dyed with 1% shade standardized? and how is it compared? yes it is CMC value but i need some more specific reasons or knowledge?
Dear Mahin, could you be more specific in your question, mabe I can help but I need some clarifications... you want to know the exact amount of dyes on the basis of color measurement or you want to know if there exist a correlation between % of dyes and LAB coordinates?
Your question should be specific. Dye percentage during dyeing, color coordinates and material liquor ratio are fully different things.
Thanks you both sir and Dear Furferi and A. Rahman sir yes my question is exactly to have an idea about the correlation between shade % and LAB ordinates. But i have an objection with the saying of ' X fabric dyed with Y% shade' whereas ultimate dyeing effect is our goal not how much dyes used.
Based on my understanding of your question, I can offer following comments-
The dye(%) given on the weight of fabric is for convenience of dyer. Imagine a dye house which does dyeing of a cotton fabric to the tune of hudreads or thousand kgs in a year. The dyeing recipe becomes a bench mark for a target shade ( at this time the correction of the shade is a different issue, that every dyer does based on his experience and delta E, L,a or b values of the target sample). Since each class of dye has a practical limit of exhaustion ( i.e. amount of dye absorbed by fabric). Calculation of amount of dye absorbed is not only impractical but impossible in an industrial scenario. However, it might be a valid and important measurement for research purpose.
As regards the material to liquor ratio, it is logical that for the same dye amount ( i.e % shade) the increase in material to liquor ratio will cause lesser uptake of the dye. hence in a dye house it is a common practice to set the dye recipe and operating parameters which are followed strictly during production as well as during shade development for spectrophotometer database. I hope this comment is helpful for you.
I agree with Dr. Patil. Spectrophotometry is used to assess the colour of fabrics after the dyeing has been made. For some kind of fabrics it is roughly and experimentally possible to define a "trasnfer function" between spectrophotometric values (e.g. CIELab values) and final shading of the fabric. but there is no mathematical relationship becouse of the different characteristics of fibers, different materials etc. In some of my works we used Artificial Neural Networks to relate the percentages of colours used for some recipes with the spectrophot. response. This is just an example.
Best
Does anyone know how much dye, in wt% of the fibers, is used on average? Just a "rule of thumb" from the industry would already help me a lot.
Dear Marianne,
This depends e.g. on the type of fibre to be dyed as well as on the depth of shade. Therefore the range of dyestuff used may vary e.g. between around 0.2 and 10 % o.w.f.
Helga Thomas , thank you for your swift reply! Can this range be narrowed down for disperse dyes on polyester fibers?
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