A terra cotta clay fired from cone 06 (bottom) to 4

Thursday 1st December 2016

insight-live.com/glossary/88">Terra cotta bodies are more volatile in the kiln than stonewares. They mature rapidly over a narrower range of temperatures, that process is accompanied by dramatic changes in fired color, density and fired strength. These bars are fired (bottom to top) at cone 06, 04, 03, 02, 2 and 4. This is Plainsman BGP (a quarry material), cone 02 finds it at maximum density (and fired shrinkage). At cone 06 (1830F/1000C) it is porous and shrinks very little. But as it approaches and passes cone 03 (1950F/1070C) the color deepens and then moves toward brown at cone 02 (where it reaches maximum density and stoneware strength). However, past cone 02 it becomes unstable, beginning to melt (as indicated by negative shrinkage). This is typical of most terra cotta clay materials. The good news: With careful selection of temperature this clay can produce strong and durable pottery at a very low, and economical, temperature.

Pages that reference this post in the Digitalfire Reference Library:

Why this transparently-glazed terra cotta is better at cone 03 than 04, Vitreous fired ceramic that stays floating!, Maturity, Terra Cotta, Cone 1, Vitreous, Firing Shrinkage

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.