This part of ISO 9455 specifies a qualitative method for assessing the aggressiveness of a flux towards copper. The test is applicable to all fluxes of type 1 as defined in ISO 9454-1.
DS/ISO 9455-5:1994 history
1994DS/ISO 9455-5:1994 Soft soldering fluxes - Test methods - Part 5: Copper mirror test