What are the causes and treatments of dark and light spots?

1. dark spots

Causes:

①The oil stain on the fabric is not cleaned during pretreatment, and the oil stain is darker during dyeing.

②There is too much foam in the dyeing bath, and the mixture of foam, floral sweater, dye, etc. sticks to the fabric.

③Dark oil spots caused by floating oil of defoamer.

④The tar in the dyeing vat sticks to the fabric.

⑤Dye agglomerates to form dark spots under different conditions.

⑥ Water quality is caused by excessive calcium and magnesium ions combined with dyes and stained fabrics.

Approach:

①Add degreaser during pretreatment for scouring.

②The dyeing auxiliaries adopt low-foaming and non-foaming auxiliaries.

③Select the defoamer that is not easy to float, add a chelating agent to improve water quality, and add a solubilizing dispersant to prevent dye aggregation. Use the tank cleaning agent to clean the tank and wash the tank in time.

2. Light spots

Causes:

①The pre-treatment is uneven, and the hair effect of some parts is not good, resulting in a certain degree of repellency, with repellent substances. Calcium soap, magnesium soap, etc. or uneven mercerization on the cloth during pretreatment.

②Uneven drying of semi-products.

③The cloth surface is stained with undissolved sodium sulfate, soda ash and other solids.

④Drip water before drying the dyed material.

⑤Auxiliary stains on light-colored objects after softening treatment, etc.

Approach:

Strengthen the pre-treatment. When selecting pre-treatment auxiliaries, calcium-magnesium soap must not be easily formed, and the pre-treatment must be uniform and thorough (this is related to the selection of scouring agents, penetrants, chelating dispersants, mercerizing penetrants, etc.). Sodium sulfate, soda ash, etc. must be properly mixed into the tank, and production management must be strengthened.