Dehydroxylation in kaolin (in the ceramic firing process)

50-250C (122-482F) | 80-250C (176-482F) | 120C (248F) | 150C (302F) | 180C (356F) | 185C (365F) | 200-450C (392-842F) | 200-1000C (392-1832F) | 200C (392F) | 210-280C (410-536F) | 260C (500F) | 290C (554F) | 300C (572F) | 300-330C (572-626F) | 300C (572F) | 370-700C (698-1292F) | 370C (698F) | 400C (752F) | | 425-650C (797-1202F) | 470-1200C (878-2192F) | 500-600C (932-1112F) | 512C (953F) | 540-600C (1004-1112F) | 650-900C (1202-1652F) | 750-850C (1382-1562F) | 750-1000C (1382-1832F) | 760C (1400F) | 760C (1400F) | 787C (1448F) | 800-1100C (1472-2012F) | 815C (1499F) | 815C (1499F) | 843C (1549F) | 850C (1562F) | 850-950C (1562-1742F) | 850C (1562F) | 870-900C (1598-1652F) | 871C (1599F) | 900C (1652F) | 900-1000C (1652-1832F) | 900C (1652F) | 926C (1698F) | 932C (1709F) | 950-1050C (1742-1922F) | 954C (1749F) | 980C (1796F) | 982C (1799F) | 990C (1814F) | 1025C (1877F) | 1025-1325C (1877-2417F) | 1050-1200+C (1922-2192F) | 1050C (1922F) | 1065-1120C (1949-2048F) | 1082C (1979F) | 1100C (2012F) | 1100C (2012F) | 1100C (2012F) | 1100C (2012F) | 1300C (2372F) | 1325C (2417F) | 1330C (2426F) | 1360C (2480F) | 1418-1428C (2584-2602F) | 1420C (2588F) | 1510C (2750F) | 1550C (2822F) | 1565C (2849F) | 1650C (3002F) | 1785C (3245F) | 1990C (3614F) | 2300C (4172F) | 2320C (4208F)

Also called dehydration. Water is chemically-bound into the mineral crystal structure in kaolin (also ball clays and other clay minerals). In firing of ceramic bodies, moisture is expelled during this phase. In the process of making calcined kaolin (meta kaolin) the reaction is considered finished at 600C (proceding into the spinel-type intermediate phase).

It is difficult to say when the release of physical water finishes and the release of chemically bound water begins, there is an overlap. Some texts put the beginning of the overlap as low as 100C, but that seems unlikely.

Glossary	Calcination Calcining is simply firing a ceramic material to create a powder of new physical properties. Often it is done to kill the plasticity or burn away the hydrates, carbonates, sulfates of a clay or refractory material.
Temperatures	Hygroscopic water removed in clay bodies (50-250)
Temperatures	Metakaolin converts to spinel phase (950-1050)
Temperatures	Spinel phase meta kaolin converts to mullite (1050-1200+)
Minerals	Mullite Mullite (3Al₂O₃·2SiO₂) is a naturally occurring aluminum silicate crystalline mineral. It forms in h

400-600C (752-1112F)

Dehydroxylation in kaolin

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