Vat dyeing is one of the oldest methods of dyeing and was mainly used with indigo dyeing. The dyeing is done in a vat or tub. If using vat dyes, it is a long process and with the advent of chemical dyes is used only in particular instances and places, especially where traditional blue patterns or fabric are produced. (But, technically, any dyeing done by immersing the yarn or fabric in a dye solution in a tub can be referred to as vat dyeing even if vat dyes are not used.)