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•The secret to cool bodies and glazes is a lot of testing.
•The secret to know what to test is material and chemistry knowledge.
•The secret to learning from testing is documentation.
•The place to test, do the chemistry and document is an account at https://insight-live.com
•The place to get the knowledge is https://digitalfire.com
| If this formula is not unified correctly please contact us. | |||||||||||||||||||||||||||||||||||||
| PCE - Pyrometric Cone Equivalent | 29-30 |
| SVWT - Sieve Analysis Wet | on 28 mesh: 1% 35 mesh: 6.5% 48 mesh: 9.0% 65 mesh: 8% 100 mesh: 12.5% 150 mesh: 12.0% 200 me |
This once popular (but variable) fire clay has not been available for many years. It occurs in many clay body recipes and common substitutes are Hawthorn Bond (likely the best) and AP green fire clay. However this is not a refractory material, it has about the same vired maturity at a typical cone 10 brown iron stoneware (or even more vitreous). Porosity is 2% at cone 10R and 10 oxidation. Fired shrinkage is 5.7% at cone 10. At cone 7 porosity is 4% with 5.2 shrinkage. Drying shrinkage is 5.8%, so this is not a highly plastic material like some fireclays (it has about the plasticity of a typical pottery clay).
Very different chemical analyses have been presented for this material.
For example, another lists SiO2 as 70.8 and Al2O3 and 25.4 with no LOI?
Example of the lignite particles in a fireclay (Pine Lake) that have been exposed on the rim of a vessel after sponging. This is a coarse clay, but if it were incorporated into a recipe of a stoneware, glaze pinholing would be likey.
Fired to cone 10R (top) and 7,8,9,10 oxidation (from bottom to top).
Out Bound Links
Hawthorne Fireclay, Hawthorn, HAWTHORN 35m
AP Green, A.P., A. P., APG Fire, APGFC
Fire Clay
By Tony Hansen
