Dasteck ChemicalsYantai Dasteck Chemicals Co., Ltd.
Direct answer
The three most common complaints after switching to thiourea dioxide are uneven dyeing, shade shift and strength loss. The root causes differ, so the table below is the fastest way to locate them.
Troubleshooting table
| Complaint | Most likely cause | First fix |
|---|---|---|
| Uneven dyeing, cloudiness | Alkali or reducing agent added too fast, causing local over-concentration; poor agitation | Add in portions, alkali first, then the product; ensure circulation |
| Shade shift | Over-reduction from excessive dose, temperature or time; possibly too much alkali | Reduce the dose first, then temperature or time, then alkali |
| Strength loss | Cellulose or protein hydrolysis from high temperature combined with high alkali; protein fibres are especially sensitive | Lower temperature and alkali, shorten time; measure strength retention |
| Uneven stripping | Insufficient liquor ratio or fabric stacking causing local concentration differences | Increase the liquor ratio, improve circulation, extend the time |
| Insufficient whiteness | Temperature below 70 °C or insufficient alkali | Raise above 70 °C and top up the alkali |
General handling sequence
1. Reproduce first: take the same fabric or pulp batch and run the customer's recipe in full
2. Single-variable comparison: change only one of dose, temperature, alkali or time
3. Quantify: shade as delta E, unevenness by rating, strength as retention, whiteness as ISO value
4. Give the corrected recipe and the reason, not just the conclusion
One rule of thumb
If the customer reports a shade shift after switching, check the dose and temperature first in nine cases out of ten, rather than blaming the dye. Reducing the dose usually fixes the shade and the cost at the same time.
Sources
The logic follows our technical data sheet and the comparative process data in published literature.