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I am not a safety expert, or a chemist. Do not use this site as a primary source for safety, chemistry or disposal information.



  • Calcium Chloride - Wikipedia
    • CaCl2
    • Calcium chloride has a very high enthalpy change of solution. A considerable temperature rise accompanies its dissolution in water. The anhydrous salt is deliquescent; it can accumulate enough water in its crystal lattice to form a solution.
    • Calcium chloride is used to increase the water hardness in swimming pools.
    • Solubility in water, g/100ml at 20°C: 74.5
    • Calcium Chloride Handbook
    • Melting Point_ 772–775 °C (1,422–1,427 °F)
    • Boiling Paint_ 1,935 °C (3,515 °F) It appears that left to its own devices this material will not decompose in our kilns. I am not sure that this is true. However when it works itself into a glassy melt we should expect that the chlorine will be expelled.
  • Calcium Sulphate and related hydrates Plaster of Paris, dead burned plaster ludo etc. - Wikipedia
    • Solubility 0.24 g/100ml at 20 °C (dihydrate)
    • Read about dehydration and temperatures on Wikipedia
    • Plaster of Paris here
    • Melting point 1,460 °C (2,660 °F; 1,730 K) (anhydrous)
    • Decomposition is aided by presence of silica and alumina page 10 . I have always assumed that when melted in a glassy melt there is little ability to hold the sulphur dioxide and that it comes off and can be a source of bloating and pinholes. Richard Burkett suggested that decomposition can be aided by reduction of a kiln at or above 1500 F to Calcium Sulfite. The sulfite melts at600 °C (1,112 °F; 873 K) . I am convinced that calcium sulphate is a source of gases causing pinholing and bloating.
    • Calcium Sulphate is the chemical usually seen as scumming on ceramics. If you want it gone you can try treating your clay with small amounts of Barium Carbonate. In my soda kiln however, calcium sulphate scumming was something I looked forward to. I have considered wedging small amounts of the powder into my clay. I have some data to show that this would be interesting.
  • Calcium Hydroxide - Slaked Lime
    • used as a cementatious binder in mortars and whitewash
    • reacts with atmospheric carbon dioxide or sodium carbonate to become Calcium Carbonate (limestone)
    • normally made by combining or slaking the highly reactive and dangerous quicklime (Calcium Oxide) in water. This reaction can happen explosively fast. It releases a great deal of heat, often enough to convert the excess water involved into steam and blow up in your face. This can happen if you use pure calcium carbonate as wadding and is more likely to be dangerous at earthenware temperatures. At higher temperatures I assume that its the impurities that usually cause it to sinter enough to slow the reaction. PLEASE be careful if messing with calcining calcium carbonate. Eye and respiratory protection are a must.
  • Ulexite
  • GerstleyBorate
    • Gerstley bearing slips in clays seems to cause a calcium scum on the surface.
    • Calcia Oh Calcia

I am not a safety expert, or a chemist. Do not use this site as a primary source for safety, chemistry or disposal information.

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