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.
Category: Kiln Wash
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.
Will Kiln Washing ADVANCER® Shelves or Getting a Few Drops of Water on Them Cause a Problem?
No. It takes prolonged exposure to a continuous moisture source to cause problems. It should also be noted that there is no evidence of atmospheric humidity causing moisture problems with ADVANCER® shelves. They are in use almost everywhere in the world!