The use of a copolymer (A) preparable by free-radical polymerization of a) at least one olefinically unsaturated monomer and b) at least one olefinically unsaturated monomer different than the olefinically unsaturated monomer (a) and of the general formula I R1R2C═CR3R4  (I), in which the radicals R1, R2, R3 and R4 each independently of one another are hydrogen atoms or substituted or unsubstituted alkyl, cycloalkyl, alkylcycloalkyl, cycloalkylalkyl, aryl, alkylaryl, cycloalkylaryl, arylalkyl or arylcycloalkyl radicals, with the proviso that at least two of the variables R1, R2, R3 and R4 are substituted or unsubstituted aryl, arylalkyl or arylcycloalkyl radicals, especially substituted or unsubstituted aryl radicals; in an aqueous medium, in a coating material used to produce surfacer coats and antistonechip primer coats.