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A melt fluidity comparison between two cone 6 matte glazes. G2934 is an MgO saturated boron fluxed glaze that melts to the right degree, forms a good glass, has a low thermal expansion, resists leaching and does not cutlery mark. G2000 is a much-trafficked cone 6 recipe, it is fluxed by zinc to produce a surface mesh of micro-crystals that not only mattes but also opacifies the glaze. But it forms a poor glass, runs too much, cutlery marks badly, stains easily, crazes and is likely not food safe! The G2934 recipe is google-searchable and a good demonstration of how the high-MgO matte mechanism (from talc) creates a silky surface at cone 6 oxidation the same as it does at cone 10 reduction (from dolomite). However it does need a tin or zircon addition to be white.
G2934 is a popular matte for cone 6 (far left). The mechanism of the matteness is high MgO content (it produces a more pleasant surface that cutlery marks and stains less than other mechanisms such as crystallization). But what if it is too matte for you? This recipe requires accurate firings, did your kiln really go to cone 6? Proven by a properly set firing cone? If it did, then we need plan B: Add some glossy to shine it up a bit. I fired these ten-gram GBMF test balls of glaze to cone 6 on porcelain tiles, they melted down into nice buttons that display the surface well. Top row proceeding right: 10%, 20%, 30%, 40% G2926B added (100% far right). Bottom: G2916F in the same proportions. The effects are similar but the top one produces a more pebbly surface.
Glossary |
Matte Glaze
Random material mixes that melt well overwhelmingly want to be glossy, creating a matte glaze that is also functional is not an easy task. |
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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 |
Food Safe
Be skeptical of claims of food safety from potters who cannot explain or demonstrate why. Investigate the basis of manufacturer claims and labelling and the actual use to which their products are put. |
Glossary |
Crystallization
Ceramic glazes form crystals on cooling if the chemistry is right and the rate of cool is slow enough to permit molecular movement to the preferred orientation. |
Glossary |
Glaze Recipes
Stop! Think! Do not get addicted to the trafficking in online glaze recipes. Learn to make your own or adjust/adapt/fix what you find online. |
Oxides | ZnO - Zinc Oxide |
Articles |
Trafficking in Glaze Recipes
The trade is glaze recipes has spawned generations of potters going up blind alleys trying recipes that don't work and living with ones that are much more trouble than they are worth. It is time to leave this behind and take control. |
Recipes |
G2934 - Matte Glaze Base for Cone 6
A base MgO matte glaze recipe fires to a hard utilitarian surface and has very good working properties. Blend in the glossy if it is too matte. |
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