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The shelf on the right in the traditional kaolin:silica kiln wash. Flaking constantly. Sticking on the feet of ware. A real aggravation. The one on the left is L4001, it is perfectly even. Yet thin. Much more refractory so it has not hardened or become brittle. Or cracked. And it paints on beautifully. The secret? Zircon. Zircopax, to be precise. Zircopax is among the most refractory materials in ceramics. We mixed it with some calcined, rather than raw kaolin. That greatly reduces drying and firing shrinkage and helps densify and stabilize the coverage (by its flat particle shape). Laguna gum solution was added to harden the dry layer and slow down the drying (their gum solution has a higher percentage of CMC than achievable using common mixing methods). Click the link below to get the recipe.
A high-melting powder applied to kiln shelves to prevent ware from sticking to the shelf during firing. It is also used as a parting agent for to keep elements of fired ware from sticking to each other.