Ceramic Materials

•The secret to cool bodies and glazes is alot of testing.
•The secret to know what to test is material and chemistry knowledge.
•The secret to learning from testing is documentation.
•The place to test, do the chemistry and document is an account at https://insight-live.com
•The place to get the knowledge is https://digitalfire.com

Sign-up at https://insight-live.com today.


Formula: 2CaO.3B2O3.5H2O or CaB3O4(OH)3·H2O

Oxide Weight160.49
Formula Weight205.49
If this formula is not be unified correctly please contact us.
DENS - Density (Specific Gravity) 2.95
HMOH - Hardness (Moh) 4.5
GSPT - Frit Softening Point 1050C
SLBY - Solubility in HCl but not in water

Colemanite has been a popular natural source of insoluble boron for many decades. It is similar to Ulexite in its oxide contribution to glazes (although the latter sources Na2O also). Frits are used as boron sources in industry whereas potters and smaller companies have used colemanite.

Colemanite does not melt as low or as uniformly as Ulexite. Gerstley Borate contained significant amounts of colemanite. Pure colemanite, however, is much higher in B2O3 than Gerstley Borate.

Colemanite is available from Turkey, Chile and California. The chemistry of these varies quite a bit, and of course, none of the available materials have the theoretical chemistry shown here.

Very high percentages of colemanite in a glaze can result in wrinkling of the fired surface, likely due to to a phenomenon called 'decrepitation' that occurs when colemanite is heated. Be sure to screen out any materials coarser than 200 mesh, or ball mill the glaze. Gum or other binders also help.

Out Bound Links

In Bound Links

By Tony Hansen

XML for Import into INSIGHT

<?xml version="1.0" encoding="UTF-8"?> <material name="Colemanite" descrip="" searchkey="" loi="0.00" casnumber="1318-33-8"> <oxides> <oxide symbol="CaO" name="Calcium Oxide, Calcia" status="" percent="27.300" tolerance=""/> <oxide symbol="B2O3" name="Boric Oxide" status="" percent="50.800" tolerance=""/> </oxides> <volatiles> <volatile symbol="LOI" name="Loss on Ignition" percent="21.900" tolerance=""/> </volatiles> </material>

Feedback, Suggestions

Your email address


Your Name


Copyright 2003, 2008, 2015 https://https://digitalfire.com, All Rights Reserved