This document specifies general methods, with suitable test conditions, for the determination of the ash of a range of plastics (resins and compounds). The particular conditions chosen may be included in the specifications for the plastic material in question. Particular conditions applicable to poly(alkylene terephthalate) materials, unplasticized cellulose acetate, polyamides and poly(vinyl chloride) plastics, including some specific filled, glass-fibre-reinforced and flame-retarded materials, are specified in ISO 3451-2, ISO 3451-3, ISO 3451-4 and ISO 3451-5.