Disclosed are methods of lowering application viscosities of or of reducing or eliminating monomer content in electrical impregnating materials comprising or consisting of an emulsion of an unsaturated polyester or a mixture of unsaturated polyesters, water, at least one radical polymerization initiator or radical polymerization initiator/promoter mixture, at least one surfactant having an HLB-value of greater than 15, optionally at least one reactive diluent, and optionally further additives, a process for preparing zero or low VOC electrical impregnation materials, a method of impregnating electrical or electromechanical devices and a method of increasing the stability of aqueous emulsions of unsaturated polyesters.