Sulfur Black：C.I.NO.Bk1

Sulfur Black is one of the most widely used black dyes in the textile industry, particularly for dyeing cotton and other cellulosic fibers such as linen, viscose, and hemp. It accounts for approximately 75–85% of all sulfur dyes produced globally due to its excellent cost-effectiveness, deep black shade, and good fastness properties.

Key Properties

Sulfur Black is insoluble in water. To make it applicable for dyeing, it must be reduced in a solution of sodium sulfide (Na₂S), which converts the dye into a water-soluble leuco form. Once the fiber is immersed, the dye is re-oxidized in air or by using an oxidizing agent, resulting in a deep black color with good wash and light fastness.

Main Applications

This dye is primarily used for cotton textiles, denim, workwear, and industrial fabrics where a deep, economical black is required. It is also used in the production of sewing threads, canvas, and shoe linings. Its ability to produce uniform, dark shades at a low cost makes it especially popular in mass-produced garments.

Critical Drawback: Tendering (Brittleness)

The most significant issue with Sulfur Black is the "tendering" effect. Over time, especially under warm and humid conditions, residual sulfur compounds in the dyed fabric can oxidize into sulfuric acid (H₂SO₄). This acid attacks the cellulose chains, causing the fabric to become brittle and lose tensile strength. To prevent this, post-dyeing treatments such as anti-tendering agents (e.g., urea, sodium acetate, or softeners) are essential.

Modern Variants

To address environmental and quality concerns, new forms have been developed, including water-soluble Sulfur Black (which reduces the use of sodium sulfide) and liquid Sulfur Black (which contains fewer impurities and is easier to handle).

In summary, Sulfur Black remains an indispensable dye for the textile industry due to its low cost and deep color .

Hot Tags: sulfur black：c.i.no.bk1, China sulfur black：c.i.no.bk1 manufacturers, suppliers, factory