Glaze Variegation Property
In contrast to the typical homogeneous surfaces of sanitaryware and most table ware, reactive glazes exhibit discontinuities in texture, matteness, reflectivity, color, etc that are called variegation. These variations are normally caused by crystallization, speckling and rivulets and opacity variations associated with phase separation. By understanding these mechanisms it is possible to produce glazes of more interesting appearance.
Mechanisms
| Oxides | ZrO |
|---|---|
| Oxides | Li2O |
| Oxides | CaO |
| Materials | Iron Oxide Red |
| Oxides | P2O5 |
| Materials | Ilmenite |
| Materials | Rutile |
| Materials | Iron Pyrite |
| Materials | Granular Ilmenite |
| Materials | Granular Rutile |
| Materials | Tin Oxide |
| Materials | Titanium Dioxide |
| Oxides | TiO2 |
Variegation and phase separation with about 5% rutile
The glaze is a dolomite matte fired to cone 10R. High fire reduction is among the best processes to exploit the variegating magic of rutile.
Links
| Articles |
Variegating Glazes
This is an overview of the various mechanisms you can employ to make glazes dance with color, crystals, highlights, speckles, rivulets, etc. |
|---|---|
| Glossary |
Dolomite Matte
Dolomite matte glazes have the potential to be very silky and pleasant to the touch, while at the same time being hard, durable and non-crazed (if they are formulated correctly). |
| Glossary |
Reduction Firing
A method of firing stoneware where the kiln air intakes and burners are set to restrict or eliminate oxygen in the kiln such that metallic oxides convert to their reduced metallic state. |
| Glossary |
Reactive Glazes
In ceramics, reactive glazes have variegated surfaces that are a product of more melt fluidity and the presence of opacifiers, crystallizers and phase changers. |
| Glossary |
Opacifier
Glaze opacity refers to the degree to which it is opaque. There is more than meets to eye to the subject of opacity control. |
| 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 |
Crystalline glazes
A type of ceramic glaze made by potters. Giant multicolored crystals grown on a super gloss low alumina glaze by controlling multiple holds and soaks during cooling |
| Glossary |
Phase Separation
Phase separation is a phenomenon that occurs in transparent ceramic glazes. Discontinuities in the internal glass matrix affect clarity and color. |
| Glossary |
Mechanism
Identifying the mechanism of a ceramic glaze recipe is the key to moving adjusting it, fixing it, reverse engineering it, even avoiding it! |
| Oxides | MgO - Magnesium Oxide, Magnesia |
By Tony Hansen 
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