Abstract: The invention is directed to a process for treating polymer-containing workpiece surfaces and to an aqueous non-aging solution. In addition to the swelling agents used for swelling, alkalizing agents and basic salts, the solution applied in the process contains at least one solubilizer for the swelling agent in the solution which is selected from the group of organic compounds having the general formula HO--A(OH)--R, where A represents a branched or unbranched alkane chain, R represents a branched or unbranched alkyl group or hydrogen, and A and R together contain at least three carbon atoms. The process and the swelling solution can be used for metallizing polymers.