Abstract: An ink, capable of producing a visible trace having a high absorption for light, said ink being an aqueous solution containing a dissolved chelate of iron or titanium and a dissolved water soluble polyhydroxy compound which includes a benzene, naphthalene or unsaturated heterocyclic ring containing as substituents at least two hydroxy groups in the ortho or peri position in regard to one another with an unsaturated bond in the ring adjacent to at least one of the hydroxy groups, the ink being sufficiently acid to prevent reaction between the chelate and the polyhydroxy compound until the ink is applied to an alkaline surface.