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On a clay test tile this titanium opacified cone 6 oxidation glaze, G1214Z1, looks great. But it is important to recognize that its variegated fired appearance is a combination multiple factors: The chemistry of the glaze, the titanium, quality laydown, the PLC6DS firing schedule, the red M390 clay body and variations in the thickness-of-application. However, the last four of those factors changed with the mug on the right! It is made from buff-burning M340! There are drips from uneven drainage during glazing. The slow cool C6DHSC firing schedule. Notice how it is actually going transparent where very thick. An even laydown was not achieved since the slurry was not properly mixed, it contains calcined kaolin and requires special attention to achieve a thixotropy.

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Watch the G1214Z video to see me convert the G1214M cone 6 clear base into G1214Z cone 6 calcium matte using simple glaze chemistry and recipe logic. This first appeared in the Digitalfire desktop Insight instruction manual 30 years ago. It is an understatement to say that this process is interesting if you want to know more about glazes, their chemistry and recipe logic. Watch this video and see me adjust the recipe of my high-calcium transparent cone 6 glaze to convert it into a calcium matte. In an Insight-live.com account, the process is easy enough for anyone. We'll cut the Si:Al ratio, increase the CaO, maintain the thermal expansion for glaze fit and make the recipe shrinkage-adjustable using a mix of calcined kaolin and raw kaolin. We will even compare it with the High Calcium Semimatte from Mastering Glazes.

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The body is Plainsman M390. Firing is the cone 6 PLC6DS schedule. Each horizontal row is a commonly-used base glaze. The top one is an MgO matte, the next one down is a calcium matte, row 3 is G2926B glossy and row 4 is Ravenscrag Slip+frit. The two mattes behave very differently from each other with the additions of opacifier. Thickly applying an opacified glaze will obviously affect visual character (column 4). Tin oxide fires whiter than zircon (e.g. Zircopax). If you like the G2934 recipe, consider the G2934Y variant for better melting.
| Materials |
Titanium Dioxide
A super white powder used in ceramic glazes to variegate, opacify and moderate color. |
| Glossary |
Opacifier
Glaze opacity refers to the degree to which it is opaque. Opacifiers are powders added to transparent ceramic glazes to make them opaque. |
| Glossary |
Glaze laydown
Refers to the quality of the dried ceramic glaze layer and how this affects the fired result: e.g. density, hardness, evenness, thickness, freedom from defects, etc. |
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