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It will be interesting to see who is right. Here is what I think about cone 6 mattes and have found:
-Assuming they are not matte because they are simply not melted enough, they need a strong flux to melt properly (KNaO, B2O3, Li2O3, ZnO).
-Matte glazes can have a high SiO2:Al2O3 ratio if they are very melt fluid (containly lots of flux) and normally highly glossy but are cooled slowly so that crystals cover the surface and matte it. CaO, SrO work this way. Even BaO. But these run. These craze. The surface is dry, less pleasant to the touch.
-They can have high MgO (e.g. 0.4%), which creates a silky, pleasant surface. But sufficient Al2O3 is required (e.g. 0.4 or more). Typically the Si:Al ratio is low (e.g. 5.0).
-They can be matte simply by a very low Si:Al ratio (e.g. 4:1). This can craze depending on the fluxes.
-Glossy glazes can be matted by the addition of calcined alumina or magnesium carbonate. The latter won't likely craze, but glazes tend to crawl.
This biggest problem with making a matte glaze craze is that high KNaO is needed. KNaO glazes want to be very glossy.
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