Why does this bowl shape always warp in the glaze firing?
Thursday 13th March 2014
Here is an example of how a cast insight-live.com/glossary/71">porcelain piece, L3778G, warps during the glaze firing. Several factors contribute to this failure:
1. It is cast and the walls are very thin.
2. This porcelain is highly vitreous.
3. This shape has no inherent strength to resist rim warping.
Thus the following steps will help to reduce the issue: Switching to machine forming (which orients particles concentrically), reducing the feldspar in the recipe (to reduce fired maturity) or firing lower, casting thicker walls and changing to a more flared shape. There is one other option (borrowed from bone china): Fire the piece upside down on a custom alumina setter fitted to the final rim diameter - then clear glaze it at a lower temperature.
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