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Pine Lake Fireclay

Description: Plastic Pennsylvania Fire Clay

Oxide Analysis Formula
CaO 0.30% 0.02
K2O 0.50% 0.02
MgO 0.10% 0.01
Na2O 0.30% 0.02
TiO2 1.90% 0.09
Al2O3 27.30% 1.00
SiO2 58.60% 3.64
Fe2O3 1.50% 0.04
LOI 9.50%n/a
Oxide Weight 338.13
Formula Weight 373.63


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?

Related Information

Lignite can be big trouble

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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.

Pine Lake fireclay lab test bars

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Fired to cone 10R (top) and 7,8,9,10 oxidation (from bottom to top). A refractory material.


Materials Hawthorne Bond
Materials APG Missouri Fireclay
Materials Fireclay
Typecodes Fireclay
Fireclays are non-kaolin non-ball clay materials similar to stoneware clays but lacking fluxing oxides. Many fireclays have a PCE of 28 or more.


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
Pyrometric Cone Equivalent 29-30
By Tony Hansen
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