If There Are Problems Such As Color Spots And Spots, What Are The Possible Reasons? How To Remedy It?

Color spots and spots are common problems in the textile printing and dyeing process, which may be caused by factors such as process, equipment, auxiliaries, water quality or improper operation. The following is a systematic analysis of the causes and remedial measures:

I. Common causes of color spots/stains

1. Inadequate pretreatment

Reason: Incomplete desizing, refining, and bleaching lead to uneven fabric hair effect and inconsistent dye penetration.

Performance: Local color is lighter or darker, showing cloud-like patches.

2. Poor dye dissolution/dispersion

Reason: The dye is not completely dissolved (such as active dyes precipitated by hard water), or disperse dyes aggregate at high temperature.

Performance: Small color spots or stains appear on the fabric.

3. Improper use of auxiliaries

Reason: Insufficient or ineffective amount of penetrant and leveling agent leads to uneven dye distribution.

Performance: Strip or block color difference

4. Process parameters out of control

Reason: temperature changes suddenly, pH fluctuations, too small bath ratio or too fast addition of salt/alkali agent.

Performance: gradient color or dark edge and light center.

5. Equipment problem

Reason: nozzle blockage of dyeing machine, uneven pressure of rolling mill or poor hot air circulation (such as setting machine).

Performance: periodic stripes or local color difference.

6. Fabric or water quality problem

Reason: Grey cloth contains oil, dead cotton, or water hardness is too high (Ca²⁺/Mg²⁺ causes dye flocculation).

Performance: random stains or color spots.

II. Remedial measures

1. Mild color (repairable)

Re-dyeing method: Use a small amount of dye (1/5 concentration of primary color) and leveling agent, and repair at low temperature (such as 60℃ for active dye).

Stripping and re-dyeing:

Reduction cleaning: Use caustic soda + insurance powder (polyester disperse dye).

Oxidation stripping: hydrogen peroxide or sodium hypochlorite (applicable to some cotton dyes).

2. Local stain treatment

Physical removal: Use a sponge to dip in diluted acetic acid or leveling agent and gently wipe the stain (applicable to unfixed dyes).

Local oxidation: For stubborn spots, low-concentration sodium hypochlorite can be applied (fabric strength needs to be tested).

3. Process optimization prevention

Pretreatment: Strengthen desizing and refining to ensure that the wool effect is >8cm/30min.

Auxiliary adjustment: Add high-efficiency penetrants (such as isomeric tridecanol ether) to improve wettability.

Use chelating agents (such as EDTA) to soften water.

Step-by-step feeding: Salt/alkali is added in batches, and the heating rate is controlled (1℃/min).

4. Equipment maintenance

Regularly clean the dye tank and nozzle, check the flatness of the roller, and calibrate the temperature sensor.

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