Basic dyes are positively charged and work with negatively charged tissue components, while acidic dyes are negatively charged and instead work with tissue components that are positively charged. Basic dyes are constructed from cationic salts of colored bases, and acidic salts consist of salt of a sulfuric, phenolic or carboxylic organic acid.
Acidic dyes are more often used in labs as a dye bath and are effective in staining textiles because they are made up of protein fibers. These dyes bind best to animal hair such as wool or alpaca hair. Basic dyes work better with staining synthetic materials like nylon, polyester, modacrylic and olefin.