Why does this bowl shape always warp in the glaze firing?

Thursday 13th March 2014

Here is an example of how a cast porcelain piece, L3778G, warps during the glaze firing. Several factors contribute to this failure:
-It is cast and the walls are very thin.
-This porcelain is highly vitreous.
-This shape has no inherent strength to resist rim warping.
The following would help:
-Switching to machine forming (which orients particles concentrically).
-Reduce the insight-live.com/material/310">feldspar in the recipe (to reduce fired maturity).
-Fire lower.
-Cast thicker walls.
-Change to a more flared shape.
-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.

Pages that reference this post in the Digitalfire Reference Library:

Why the base of this bowl shape flattens on firing, Vitrification, Warping

This post is one of thousands found in the Digitalfire Reference Database. Most are part of a timeline maintained by Tony Hansen. You can search that timeline on the home page of digitalfire.com.