This Standard describes two methods for assessing the degree of erosion of a test film that has been exposed to weathering. These are as follows:(a) Method A -determination of the decrease in film thickness on a metal test panel as a percentage of the original dry film thickness; or(b) Method B -a visual examination to check for evidence of exposure, or 'grinning through', of an underlying substrate of contrasting colour.NOTES:1 Method A is not applicable to non-metallic substrates that prevent a determination of the film thickness using non-destructive techniques.2 Method B is usually sufficient for evaluating conventional decorative paint films, of less than 100 µm thickness, whereas Method A is suitable for heavy duty finishes of greater than 100 µm thickness.