Sulfur dyes have a history of more than a hundred years. The first sulfur dye was made in 1873 by Croissant and Bretonniere, who heated organic fibrous materials such as sawdust, humus, bran, waste cotton and waste paper with sodium sulfide and polysulfide. This dark, odorous, hygroscopic dye had no fixed composition and dissolved easily in water; dyeing cotton in an alkaline bath and a sulfide bath gave green dyeings. Exposed to air or oxidized chemically with dichromate solution for fixing, the cotton became brown. Because of their excellent dyeing properties and low price, these dyes were applied in the cotton dyeing industry.

In 1893, R. Vidal fused p-aminophenol with sodium sulfide and sulfur to make a black sulfur dye, and found that fusing certain benzene and naphthalene derivatives with sulfur and sodium sulfide produced many black dyes. Later, blue, red and green sulfur dyes were developed on this basis, and both preparation methods and dyeing technology improved continuously.

Process points for sulfur dyeing:

1. Sulfur dyes are applied from a sulfide bath at high temperature; reduction and dissolving must be complete to avoid color spots.

2. After dyeing, washing and oxidation (air oxidation or chemical oxidation) fix the color; over-oxidation can dull the shade, so it must be controlled.

3. After oxidation, soaping removes loose dye and improves fastness.

4. Sulfur dyes are sensitive to chlorine; chlorine bleaching after dyeing should be avoided or controlled.

5. Waste liquor treatment is important because sulfides in the effluent must be handled properly.

Sulfur dyes remain economical and widely used for deep shades on cotton workwear and denim.