4.1 This practice is of value (1) to the producer of fine particles as a means of reporting particle characteristics with respect to quality control and (2) to the buyer to assure that the particle size and particle size distribution meet his requirements.
1.1 This practice for reporting the fineness characteristics of pigments is designed to apply in most cases where well-known methods for determining these particle size characteristics in the subsieve range are employed, such as microscopic, sedimentation, and turbidimetric methods; and partially to absorption and permeability methods.
1.2 Laminar, plate-like pigments and composite pigments having a definite bimodal distribution are not considered within the scope of this practice.