Mar . 09, 2024 12:30 Back to list

Problems in Denim Color: Sulfur Black

Sulfur black is an important dye in denim and suppliers who produce the highest quality of black enjoy strong business with good prices. Unfortunately, sulfur black dyeing of cotton on continuous machines usually results in significant problems that cause customer dissatisfaction.

Sulfur dyes are the most difficult dyes to apply continuously and often dye machines are not designed well for applying them. Sulfurs, as well as Indigo, are known as substantive dyes which means that they attach to cotton at a faster rate than water and there are variables such as temperature, ph, ORP, moisture, preparation and even drying that need to be controlled within limits. Dyeing with sulfurs appears simple, but is similar to playing chess in the need to pay attention to all factors involved constantly.

Some of the objections to sulfur black include depth of color, resistance to fading after washing, ageing- resulting in fabric strength loss in storage (which can be predicted by using AATCC Test Method #26) staining and crocking, especially the effects on upholstery. In terms of appearance, bright shades of black are preferred to dull blacks, the bright also being more colorfast, having a greenish tone instead of a reddish tone. There are often also problems with odors, skin irritation and metal corrosion (silver jewelry turning black from free sulfur).

If the dye has a high pH, most of the dye will not attach to the cotton and is washed off, sometimes up to 70% of the dye coming off in wash-boxes, resulting not only in great economic loss, but a serious water treatment problem.

All of these problems have been solved in the past, but do require a more detailed management of dyeing than is usually observed as well as a complete understanding of sulfur dye chemistry, which has been basically lost.

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Problems With Dyeing Of Sulphur Dyes