a marking ink for glass and ceramic substrates is disclosed which can be deposited from a liquid dispersion and heat - cured rapidly to provide an insoluble adherent film . the adhesive binder for the marking ink is an inorganic cement produced by heat - reaction between phosphoric acid and an aluminum salt of a weak organic acid to form an insoluble vitreous matrix in the final product . various liquid dispersions for said marking ink are disclosed which are particularly suitable for application as indicia means upon the glass envelope of an electric lamp and can be applied during conventional lamp manufacture .