Abstract: The present invention provides a test method for simulating outdoor exposure conditions for testing a coated substrate to evaluate environmental etching of paint caused by acid rain. The test method requires that the test substrate have an acid solution having a pH of less than 6.0 applied thereto by spray or in atomized droplets. The substrate is held in a substantially horizontal position of less than 15° to the horizontal and exposed to heat of above a black panel temperature of 30° C. and light during testing. The light source must emit light in the spectral distribution of at least visible and ultraviolet light, including the spectral distribution of sunlight. Following exposure to testing the substrate is evaluated for environmental etch.