Color changing compositions using acids

摘要

A multiple coloring composition system is disclosed whose coloring effect is changed upon treatment with an overcolor, once the overcolor coloring composition has been deposited over the undercolor coloring composition. The multiple ink system comprises: (a) an undercolor aqueous coloring composition comprising an undercolor dye whose coloring ability is destroyed in the presence of an acid; and (b) an overcolor aqueous coloring composition comprising a colorant capable of maintaining its characteristic color in the presence of a pH of about 4 or less; and an acid sufficient to bring the pH of the overcolor composition to about 4 or less.