Kaolin (china clay)
Also: kaolin, china clay
A layered aluminosilicate clay used as a paper coating pigment, particularly for glossy and gloss-control coated papers.
Kaolin (Al2Si2O5(OH)4) is mined from deposits in Brazil, Georgia (US), and Cornwall (UK). Its plate-like particles align flat in a coating, producing high gloss when calendered. Coating kaolins are graded by particle size distribution and brightness.
Kaolin has lost market share to calcium carbonates in recent decades but remains essential for high-gloss coated papers and for rotogravure grades that need print smoothness without calcium carbonate's chalking tendencies.
Related
- GCC (ground calcium carbonate). A paper filler and coating pigment made by grinding limestone. The most-used inorganic additive in paper worldwide.