Vat dyes are a class of dyes that are classified by their method of application. Vat dyeing refers to the process of dyeing in a vat or bucket. Most dyes, such as fiber-reactive dyes, direct dyes, and acid dyes can be used in a vat dyeing. Cotton, wool, and other fibers can be dyed with vat dyes.https://www.alfa-chemistry.com/products/vat-dyes-114.htm