When did dye specks or shade changes first appear?
Shade at discharge reflects the dyeing stage. Subsequent heat setting can cause migration or a hue shift.
Compare the as-dyed fabric with heat-set samples
From the same roll, retain as-dyed fabric, specimens heat-set under production conditions and a control. Record time, temperature and auxiliaries. If the shift appears only after setting, investigate the thermal stage first.
Why does the shade change during heat setting?
Check thermal migration and sublimation. Compare specimens using the actual setting programme. Polyester exhaust dyeing: Trial-dye identical greige fabric at the same liquor ratio and process. Compare levelness and shade depth. Heat-set articles: Across the actual heat-treatment window, test sublimation staining and hue shift.
Checking Relative strength and Dispersibility or filterability
Relative strength (%): Compare with a reference of the same shade using the specified polyester. Dispersibility or filterability (Filter residue or rating): Identify the dispersion medium, temperature and filter material. Sublimation fastness (Grade): Specify heat treatment conditions and adjacent fabric.
What to record
- Disperse dye shade code
- Substrate
- Heat-setting profile
- Color difference before setting
- Color difference after setting
Technical references
Products and processes
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