EGECat® CopperOct and EGECat® PotassiumOct serves as synergistic with cobalt promoters in unsaturated polyester resin curing. It reduces the “pinking” effect of cobalt while alters the gel time and the exohtermic temperature peak at the curing. Although they both exhibit synergytic effect with cobalt accelarators, the former is rather an inhibitor and the latter works as promoter.