Abstract: A heat-curable composition comprises—from 25 to 65% by weight of a mixture of epoxy-functional monomers, said mixture consisting of at least one polyfunctional epoxy monomer selected from monomers comprising from 4 to 8 glycidyl groups and/or cycloaliphatic epoxy groups, and at least one bi- or tri-functional epoxy monomer selected from monomers comprising two or three glycidyl groups and/or cycloaliphatic epoxy groups, —from 25 to 70% by weight of at least one organic solvent selected from glycol monoethers, —from 2.5 to 5% by weight, relative to the total weight of epoxyfunctional monomers (a) and (b), of at least one blocked strong acid catalyst, said heat-curable composition not containing any non-epoxyfunctional monomers, in particular not containing any acrylic, methacrylic or silane monomers.