The amount of this attraction is known as "substantivity": the higher the substantivity the greater the attraction of the dye for the
fiber. Substantive dyes work best on textiles with high contents of cellulose, such as cotton. In contrast to direct dyes, wool and leather goods are dyed by the process of
ion exchange, exploiting the cationic nature of proteins near neutral pH. The development of substantive dyes helped make
mordant dyes obsolete. ==Gallery==