example demonstrates the improved optical properties obtained by controlling the particle size distribution of the hydrous kaolin fed to the process and other parameters of leaching process the process includes the following steps b pre pulverizing the spray dried feed by an air impact pulverizer d leaching with naoh solution at different concentrations for 2 hours at 180 u00b0 f 82 u00b0 c and e washing filtration drying and post pulverization with a mikro pulverizer u00ae mill with a 0 039 inch round hole screen for the preparation of fractionated feeds a hydrous kaolin feed normally used to make ansilex 93 u00ae calcined kaolin pigment was used as the standard calcination feed the standard feed at 57 8 solids was centrifuged for 10 minutes at 1000 rpm to obtain a feed cut having a particle size distribution with 92 wt lt 1 u03bcm nominally referred to as the 90 feed the same standard feed was centrifuged for 5 minutes at 1000 rpm to obtain a feed cut having a particle size distribution with 86 wt lt 1 u03bcm nominally referred to as the 85 feed another sample of the same feed was centrifuged for 30 seconds at 1000 rpm to obtain a feed cut having a particle size distribution with.