Bleached wash problem on knit /denim and solution

 

The yellowish effect on the bleached dots fabric could be due to several reasons related to the washing processes used. Here are some potential causes and solutions to address the yellowing:

Potential Causes:

1. Chemical Residues:
• Silicon Wash: Silicone-based softeners can sometimes leave a yellowish tint if not properly rinsed out.
• Enzyme Wash: Improper neutralization after enzyme treatment can cause yellowing.
• Garment Wash: The type of detergent and the pH balance during washing could affect the color.
2. Water Quality:
• High iron content in the water can cause yellowing, especially when combined with bleach.
3. Bleach Residues:
• Incomplete removal of bleach can result in yellowing over time.
4. Heat Exposure:
• High drying temperatures can cause certain chemicals to oxidize, leading to yellowing.

Solutions:

1. Rinse Thoroughly:
• Ensure that the fabric is thoroughly rinsed after each washing stage to remove any chemical residues.
2. Use Antioxidants:
• Adding antioxidants during the rinse process can help prevent oxidation and subsequent yellowing.
3. Adjust pH:
• Ensure that the pH is neutralized properly after each wash. A slightly acidic final rinse (pH 5.5-6.5) can help prevent yellowing.
4. Water Quality:
• If the water has a high iron content, using a water softener or iron remover could help.
5. Lower Drying Temperature:
• Reduce the drying temperature to prevent heat-induced yellowing.
6. Use Optical Brighteners:
• Incorporating optical brighteners in the final rinse can help maintain the fabric’s brightness.

Recommendations for Future Production:

1. Test Washes:
• Conduct small-scale test washes with different combinations of washing treatments to identify the cause of yellowing.
2. Chemical Quality Control:
• Ensure that the chemicals used in the washing process are of high quality and suitable for the fabric type.
3. Process Optimization:
• Work with your chemical supplier to optimize the washing process and chemical formulations to prevent yellowing.

By systematically adjusting these variables, you should be able to eliminate the yellowish effect and maintain the desired appearance of the bleached dots fabric.