This document specifies general methods@ with suitable test conditions@ for the determination of the ash of a range of plastics. The particular conditions chosen can 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-fibrereinforced and flame-retarded materials@ are specified in ISO 3451-2@ ISO 3451-3@ ISO 3451-4 and ISO 3451-5.