Polyfil WC-426 clay is a white, high brightness, anhydrous organo-functional pigment designed to maximize compatibility with surrounding polymers and to minimize absorption of interfacial moisture. Mechanical and electrical properties of polymers such as EPR and cross-linked polyolefins are preserved even after long-term exposure to a high-humidity environment. Calcined clays impart have low conductivity due to the elimination of bound water during the calcined process. Compounds with calcined clays extrude smoothly and reduce stickiness in processing. Polyfil WC-426 is KaMin's highest brightness and smallest particle size treated calcined clay.