Acid dyes are water-soluble, anionic dyes primarily applied to textiles at low ph. The term “acid dye” comes from the dyeing process, which is carried out in an acidic medium (ph around 2–6) using mineral or organic acids such as sulphuric, acetic, or formic acid. Most acid dyes are sodium salts of organic acids, giving them their anionic nature. Under acidic conditions, they are strongly attracted to positively charged amino groups in fibers like wool, silk, and nylon, resulting in brilliant and uniform coloration.
