about 4 5 and 6 5 for obtainment of a product with optimum tinctorial properties the temperature range over which the coupling reaction of the invention can be conducted successfully is from about 0 u00b0 c and 50 u00b0 c to obtain pigment with maximum scattering i e high degree of hiding power in paint applications the preferred coupling temperature range is from about 5 u00b0 c to 20 u00b0 c to determine the masstone of each pigment tested 0 6 g of the pigment tested is mixed with 1 2 g of a typical lithographic varnish an air drying resin according to the procedure described in the journal of the oil and colour chemists association no 396 vol xxxvi june 1953 page 283 the masstone formulations for each pigment tested is spread on white paper and visual comparisons are made the strength of each pigment tested is determined by mixing 0 09 g of the masstone formulation with 10 0 g of a zinc oxide paste prepared by mixing 98 parts of the lithographic varnish used to prepare the masstone formulation one part of a typical varnish drier and 150 parts of zinc oxide the relative tinting strength of the pigments tested is determined visually after spreading each of the tinting formulations on white paper visual hiding occurs when a paint film is sufficiently thick to prevent one from seeing the substrate beneath the film to determine the relative visual hiding power of the pigments tested a typical paint composition containing the same pigment to binder ratio for each pigment is sprayed on conventional black and white morest chart paper the paper is coated with a thin paint film less than hiding at the top and gradually coated with thicker paint films to a point greater.