1. As direct dyes and other accelerating agents for cotton dyeing

When dyeing cotton with direct dyes, sulphur dyes, vat dyes and Yindioxin dyes, sodium sulfate can be used as a dye accelerator. These dyes are easy to dissolve in the prepared dyeing liquor, but not easy to dye cotton fibers. Because the dye is not easy to be exhausted, there is a lot of dye remaining in the foot water.

The addition of sodium sulfate can reduce the solubility of the dye in water, thereby increasing the coloring power of the dye. In this way, the amount of dye can be reduced, and the dyed color will be deepened.

2. Used as a retarder for direct dyeing and silk dyeing

The application of direct dyes on protein fibers is mostly silk dyeing, and the dyeing fastness obtained is better than that of general acid dyes. Some direct dyes also have excellent dischargeability, so they are often used for discharge of ground color in silk fabric printing. Direct dyeing of silk also often adds a small amount of sodium sulfate, but the role of sodium sulfate is different from that of cotton dyeing. It only acts as a slow dyeing agent.

3. As acid dye retarder

When acid dyes are used to dye silk, wool and other animal fibers, sulfuric acid and acetic acid are often added to promote the coloring of the pigment acid, but at the same time, the powder is also used as a retarder.

4. Used as ground color protectant for scouring of printed and dyed silk fabrics

When scouring printing or dyeing silk fabrics, the dye may be peeled off, so as to contaminate the ground color or other homogenous fabrics. For example, the addition of sodium sulfate can reduce the solubility of the dye, so there is no danger of peeling off the dye and contaminating the ground color up.