Why this transparently-glazed terra cotta is better at cone 03 than 04

Friday 10th May 2019

insight-live.com/glossary/88">Terra cotta bodies are typically fired between cone 06 and 04. That being said, many, like this Plainsman L215, develop richer color at cone 03 and fire much stronger. Glazes, of course, melt better and micro-bubbles pass through easier at cone 03. But this happens only if the body has not begun to decompose (and therefore generate a lot more gases of decomposition). Notice that crazing is beginning on the one of the left. Apparently the improved body:glaze interface and the development of better vitrification reduces the problem. Cone 03 is somewhat of a sweet-spot for this specific body, however firing higher begins decomposition processes that generate gases that disrupt the surface. Needless to say, accurate firing is needed to fire at cone 03 for ongoing success (because cone 02 is too high for this body, glaze will blister). Do you know what terra cotta actually is, if not click the link to learn more (this is a big topic).

Pages that reference this post in the Digitalfire Reference Library:

A terra cotta clay fired from cone 06 (bottom) to 4, G1916Q transparent on terra cotta body at cone 06, 05, 03, Vitrification

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.