This part of this ISO 23900 specifies a method of determining the colouristic properties of a test pigment relative to a standard, and the ease of dispersion DH_PVC-P of pigments from the differences in colour strength on dispersing colouring materials under various conditions in plasticized polyvinyl chloride (PVC-P) compounds.

The method is appropriate for use with organic and inorganic black and colour pigments and for pigment preparations.

The ease of dispersion determined in this way is valid only for the dispersion equipment, dispersion conditions and dispersion medium being used. The use of test conditions differing from those specified may give different results; this applies both to the absolute magnitude and to the relation between values of the ease of dispersion of various pigments. The subscript DH_PVC-P is therefore used to designate the value obtained as specified in this part of ISO 23900.

The principle of this part of ISO 23900 may also be used for routine quality control purposes by reference to the photometric data generated from the sheets milled at 130 °C. For quality control purposes, the ratio of pigment to TiO₂ may be agreed between the interested parties. Ratios of 1:10 for organic pigments and 0,2 to 0,5:1 for inorganic pigments are suggested as convenient and widely used standard ratios.

Annex A is informative and gives a description of a suitable basic compound.