Kaolin, also known as China clay, is an aluminium silicate clay that is valued for its whiteness and used as a filler and coating pigment in paper, paints and plastics - of which paper is the largest market. It is also used in ceramics (its second largest end-market), fibreglass and refractories. It achieves its whiteness either naturally or through extensive processing and also from its fine particle size that gives it a refractive index of 1.56. Kaolin that is suitable for paper grade applications is subjected to further processing using centrifuges and cyclones. One of the major changes experienced in the industry was the switch by paper makers from an acid-based processing route to an alkali-based route to make paper.
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