Crystalline glazed vase by Rod and Denyse Simair

This award-winning couple are-all in on crystal glazes. They have learned that success is about data. A lot of data. Thousands of pictures, hundreds of firing schedules, hundreds of recipes, endless notes all come together in the growth of crystals like these! Notice the clear background, no micro-crystals fogging it up. Notice that two fundamentally different types of crystals are being grown. Not to be ignored is the throwing skill it takes to make a porcelain piece like this, these are not small pieces.

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One secret of crystal glazes is firing schedule

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The blue line is a crystal glaze firing schedule. While it reaches the same temperature as a typical glaze firing (purple line) it is different in how it does so. Notice key differences (while cone 10 is most common for this type of glaze, we will discuss theoretical differences in a cone 6 version):
-The steep climb: Crystallization needs a clean bubble-free melt, no lingering in temperature zones where they might start prematurely.
-The steep drop to 2000F: Crystals typically grow during a long soak in the 1900–2000°F nucleation zone.
-If the temperature is simply held steady at 1950°F only one type and size of crystal would form, likely smaller and crowding out others. The ups and downs are about manipulating the thermodynamics and kinetics of crystal formation — nudging new crystals to form or existing ones to grow differently.
-Cooling and then raising the temperature in the nucleation zone can re-dissolve smaller crystals or unstable nuclei. Then, cooling again encourages new crystal nucleation, rejuvenates existing ones or even changes the pattern of their growth.
-In the upper range of the nucleation zone, faster diffusion produces larger, more spread-out crystals. In the lower range, slower diffusion produces smaller, tighter crystals or detail-rich growth.
-Crash-cool to finish: Drop melt viscosity quickly to halt all crystal formation - this preserves a clean background and prevents blurring of crystal edges.
Crystalline firings are about precision and timing: Get in fast, melt everything, play within the range where crystals want to grow to get the type, distribution and size you want - and then get out. It is not difficult to see why crystal glazers may do thousands of test firings to discover the curve that produces what they want. The nucleation zone depends on firing temperature and glaze chemistry, testing is likewise required to discover it. Meticulous record keeping is critical to success; not surprisingly, many crystal glazes do it in an account at insight-live.com.

Crystalline glazed vase by Rod and Denyse Simair

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Internationally acclaimed ceramic artists Rod & Denyse Simair have represented Canada in major exhibitions in Europe and North America. They are the recipients of the highest international honour that has been awarded exclusively for Crystalline, Le Grand Prix du Jury, at Crystallines 2005 in France. The Simairs combine their talents with Rod's elegant and masterfully thrown original porcelain designs harmoniously brought to fruition through Denyse's personally researched, formulated and fired macro-crystalline glazes. They describe their pieces as "heirloom keepsakes of aesthetically inspiring ceramic art to cherish now and for generations to come".

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URLs	https://www.simair.ca/ Rod and Denyse Simair - Crystalline glazes
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

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