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In the glaze on the left (90% Ravenscrag Slip and 10% iron oxide) the iron is saturating the melt crystallizing out during cooling. GR10-K1, on the right, is the same glaze but with 5% added calcium carbonate. This addition is enough to keep most of the iron in solution through cooling, so it contributes to the super-gloss deep tenmoku effect instead of precipitating out.

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Because this glaze employs 10% dolomite instead of 10% calcium carbonate it has a lower thermal expansion and is less likely to craze. While the dolomite is contributing MgO, which normally mattes glazes, there is not enough to do it here.
| Oxides | CaO - Calcium Oxide, Calcia |
| Glossary |
Flux
Fluxes are the reason we can fire clay bodies and glazes in common kilns, they make glazes melt and bodies vitrify at lower temperatures. |
| Glossary |
Tenmoku
Tenmoku is a kind of high temperature reduction firing ceramic glaze. Glossy, very dark brown or maroon, fluxed by iron oxide to have high melt fluidity. |
| Glossary |
Precipitation
Crystals or crystalline particles will often form over time in ceramic glaze slurries that contain slightly soluble materials. |
| Recipes |
GR10-K1 - Ravenscrag Cone 10R Tenmoku
Plainsman Cone 10R Ravenscrag Slip based glaze. It can be found among others at http://ravenscrag.com. |
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