The present invention relates to a two-component composition comprising a first component and a second component, wherein the first component being a pre-accelerated resin composition comprising an unsaturated polyester resin or vinyl ester resin and a copper2+ compound, at least one N-containing organic base selected from an amine compound and/or an ammonium salt; and wherein copper is present in an amount of at least 50 ppm (relative to the primary resin system), wherein the resin composition contains less than 0.01 mmol cobalt per kg primary resin system, the resin composition has an acid value in the range of from 0.001-300 mg KOH/g of resin composition, the molecular weight of the resin containing reactive unsaturations is in the range of from 500 to 200,000 g/mole and wherein the second component comprises a peroxide compound.