In the method of the present invention at least a portion of the surface of a plastic article (e.g., a molded article of thermoplastic polycarbonate) is contacted with (e.g., immersed in) a treatmentcomposition which includes one or more performance additives. The treatment composition contains: (i) at least one performance additive (e.g., an ultraviolet light absorber); (ii) water; (iii) at leastone carrier represented by the following general formula (I), wherein R<1> is a radical selected from the group consisting of linear or branched C1-C18 alkyl, benzyl, benzoyl and phenyl, R<2> is a ra dical selected from the group consisting of linear or branched C1-C18 alkyl, benzyl, benzoyl, phenyl and H, n is 2, 3 or 4, and m is 1 to 35; and (iv) a diol selected from at least one of linear or branched C2-C20 aliphatic diols, poly(C2-C4 alkylene glycol), cycloaliphatic diols having from 5 to 8 carbon atoms in the cyclic ring, monocyclic aromatic diols, bisphenols and hydrogenated bisphenols.In an embodiment of the present invention, the carrier is ethyleneglycol monobutyl ether, and the diol is diethylene glycol.