Developed by the Law Enforcement Standards laboratory, the report presents results from a study to determine criteria to apply to solubility testing and chemical reactivity of automotive paints and also to standardize reagent concentration and other parameters. The focus is on testing acrylic enamels used as automotive finishes, since prior to this study these paints were reported to be virtually unreactive to all solvents when subjected to solubility tests. An ancillary objective is to apply these criteria of solubility and reactivity to testing household paints. The study defines seven categories of reactivity which form the basis for specifying the extent of solubility of paints in various reagents under controlled conditions of time and temperature. A novel solubility test procedure is also developed by which acrylic lacquers, organic-dispersed enamels, and water-based enamels can be distinguished through sequential testing, a characterization not previously accomplished with solubility testing. The test involves the use of two reagents in tandem with one reagent used as an activator. This procedure represents a substantial breakthrough in the use of solubility testing for the characterization of automotive paints. Tables and charts are given.