Requirements of True Dye

Requirements of True Dye

For a substance to act as a dye certain conditions must be fulfilled and these are as follows.
• It must have a suitable color
• It must have an attractive color
• It must be able to fix itself or be capable of being fixed to the fabric
• The substrate to be dyed must have affinity for an appropriate dye and must be able to absorb it from solution or aqueous dispersion, if necessary in the presence of auxiliary substances under suitable conditions of concentration, temperature and pH
• It must be soluble in water or must form a stable and good dispersion in water. Alternatively, it must be soluble in the medium other than water. However, it is to be remembered that the pick up of the dye from the medium should be good.

The fixed dye must have fastness properties, e.g.,
• Fastness to light,
• Fastness to temperature,
• Resistance to the action of water, dilute acids, alkalis and various organic solvents and soap solution.