The document specifies the basic test procedures for the determination of the physical properties of self-skinned, high-density (typically having an overal density in excess of 100 kg/m<(hoch)3>) rigid cellular plastic materials. It also specifies the primary methods to be used for comparison of materials similar to self-skinned, high-density materials, based upon ISO test methods and using a standard test specimen thickness. It likewise permits the use of the same test methods, when found to be suitable, for the assessment of the properties of products of different thickness, when agreed upon by the supplier and the purchaser.