This part of ISO 8130 is one of a series of standards dealing with the sampling and testing of paints, varnishes and related products. It specifies a method for the determination of the tendency for the mixing of two different coating powders to result in the deterioration of the surface quality of the final coating. The results depend on the following characteristics of the coating powders: a) their chemical reactivity; b) their chemical composition; c) their melt properties. The onset of the deterioration in appearance, its nature and its extent will depend greatly on the ratio in which the powders are mixed. The test is useful in predicting the possibility of incompatibility arising from mixing different powders both during the manufacturing process and during the application of the coating powder. The nature of the deterioration in surface appearance may manifest itself in various ways, including: — change in gloss level; — the presence of pinholes, including micro-pinholes; — the appearance of orange peel; — the presence of craters; — the presence of bittiness (graininess); — the presence of colour contamination. NOTE — Deterioration in mechanical properties may also be experienced. However, this part of ISO 8130 is only concerned with changes in appearance.