Sulfur Black 1 is imperfectly understood, and the material is probably heterogeneous. It is speculated to be a polymer consisting of thianthrene and phenothiazine subunits. The so-called sulfur bake dyes are produced from 1,4-diaminobenzene and diaminotoluene derivatives.
Sulfur dyes are mainly used for the dyeing of textile cellulosic materials, or blends of cellulosic fibers with synthetic fibers such as acrylic fibers, polyamide and polyester. They can also be used for a limited number of silk and paper applications.