Vat dyes are different from reactive dyes, disperse dyes, basic dyes, acid dyes or azoic color but its application process is near similar as sulphur dyes. Vat dyes are used for coloring cellulosic fiber specially cotton fiber. It is widely used for run the dyeing process of cotton yarns which is used for producing jeans or denim product.

The word vat is come from vessel; vat dyes can be applied in a vat for coloration textile products. Vat dyes are natural coloring materials which are solubilized in a vat by the fermentation process called vatting.

Vat dyes are insoluble in water but it becomes in soluble form by vatting process. The process of converting insoluble vat dyes into soluble form is known as vatting.

Properties of vat dyes: Vat dyes have lots of properties which are required to remember before and during dyeing process. Followings are the main properties of vat dyes.

• Vat dyes are natural coloring dyes.
• Vat dyes are insoluble in water.
• Vatting process is needed for making the insoluble vat dyes into soluble form.
• Final color is developed by the oxidation process.
• Vatting is done in alkaline condition.
• Fastness properties of the dyes are excellent but its rubbing properties are not so good.
• Sometimes, it causes different types of skin disease.
• Vat dyes are mainly used for coloring cellulosic fibers.
• Stability of the color in the fiber is excellent.
• Wide range of color can be achieved by these dyes.
• Application of vat dyes is limited in practical life.
• Vat dyes are expensive in price.

So, it’s very interesting that most of the denim product is colored by vat dyes.