| Monthly Tech-Tip | No tracking! No ads! | |
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.

This picture has its own page with more detail, click here to see it.
This is the G1214Z1 calcium matte base (as opposed to the magnesia matte G2934). The clay is Plainsman M390. 5% Zircopax was added on the left (normally 10% or more is needed to get full opacity, the partially opaque effect highlight contours well). 5% tin oxide was added to the one on the right (tin is a more effective, albeit expensive opacifier in oxidation). The PLC6DS firing schedule was used.

This picture has its own page with more detail, click here to see it.
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.

This picture has its own page with more detail, click here to see it.
The clay is a buff stoneware. The upper two samples are G2934, an MgO matte. The one on the right has 10% zircon added to opacify. The bottom two are G1214Z1 (transparent version and opacified-with-zircon version). The difference is surface character is visible.
![]() |
Converting G1214M Cone 6 transparent glaze to G1214Z matte
How I converted a glossy glaze into a matte glaze by using glaze chemistry and recipe logic. |
Buy me a coffee and we can talk