Excellent, because the dye is chemically locked to the fibre.

Typical of dyes (like Remazol). In an alkaline bath, the dye undergoes an elimination reaction to form a vinyl sulfone group, which then adds across the fiber's functional groups. Result: A highly durable covalent linkage. ⚡ Key Properties

A major challenge where the dye reacts with water instead of the fibre, creating "spent" dye that must be washed away.