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Using Alumina Hydrate and Wax with ADVANCER® Shelves

As an alternative to using kiln wash, many potters use small amounts of alumina hydrate between the pot bottom and shelf surface. If using wax approximately 1 heaping tablespoon of alumina hydrate to 1 cup of wax is usually sufficient. Stir the mixture with a brush before each application to the bottom of the vessel. You may need to experiment depending on your clay body and firing temperature.

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Using Kiln Wash with ADVANCER® Shelves

While many individual customers report that they do not need to use a wash coat on their ADVANCER® shelves, we generally recommend using a suitable high alumina wash on ADVANCER® shelves – particularly in studio or classroom settings where multiple users are present.

Stoneware and earthenware clay will not stick. Porcelain clay bodies and some B-Mix clays are highly fluxed with feldspar, usually to achieve translucency. The higher the firing temperature is, the greater the potential for the flux to interact with the oxide glass layer of the shelf. The higher the feldspar content in porcelain type clay bodies, the more likely they are to stick. Pieces with trimmed foot rings supporting larger pieces such as bowls tend to stick more than broad flat-bottomed pieces. When in doubt, the best thing to do is test how the clay interacts with the bare shelf surface.

Due to the extremely low porosity of ADVANCER (less than1%) vs. conventional silicon carbide
(18% typical) and cordierite (30% typical), it is true that there is much less of a tendency for glaze to penetrate into or stick onto the ADVANCER surface. Never the less it is still possible for glaze to react with the protective oxide glass surface of ADVANCER, especially at higher temperatures, and bond onto the ADVANCER surface. Glaze drips are usually easily removed without grinding because extremely low porosity of ADVANCER. On the other hand glazes that volatilize at temperature, leaving a fine mist of glaze on the shelf may require light grinding or sanding for complete removal.

Kiln Wash Formula
The general formula we recommend for kiln wash is 50 alumina hydrate, 25 kaolin, 25 calcined kaolin – all by weight. Apply 1-2 thin layers of kiln wash letting it dry between coats. The consistency for the wash application should be like light cream or half and half, not thick like heavy whipping cream or paste. Applying wash when the shelves are warm will help accelerate the drying process. Due to the ultra-low surface porosity of <1%, the wash will ultimately dry suspended on the glass surface of the shelf and will not soak down into the body of the shelf as with more porous shelves such as cordierite.

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Does Porcelain Stick to ADVANCER® Shelves?

Due to the high amount of flux used in porcelain clay bodies (up to 50% typical) to achieve translucency, it is not uncommon for porcelain clay bodies to stick to the ADVANCER surface. The higher the firing temperature is, the greater the opportunity for the flux to interact with the oxide glass layer of the shelf. Pieces with trimmed foot rings supporting larger pieces, like bowls, tend to stick more tenaciously than broad, flat bottomed pieces due to increased pressure on contact area. Some cone 6 porcelains may not have a sticking problem on ADVANCER. Please contact us for more specific information. You may also refer to the article “Why Porcelain May Stick to ADVANCER” on this website for a more technical explanation.