Enamel coating of a coated glass substrate

A method of treating a glass substrate having a coating is disclosed, said method comprising applying a paste onto at least a portion of said coating in a desired pattern; drying said paste to form a dried paste in said desired pattern; and firing said dried paste to form an enamel in said desired pattern, said enamel being directly bonded to said glass substrate by dissolution of the portion of the coating to which the paste is applied during the firing step. The paste comprises a solids portion dispersed in a dispersion medium, said solids portion including a composition comprising: 10 to 40 mol% ZnO; 20 to 40 mol% B2O3; 25 to 65 mol% Bi2O3, TeO2, or PbO, or mixtures thereof; and to 15 mol% Al2O3.