Jordan Fireclay

Alternate Names: Maryland Ball/Stoneware Clay

Description: Low Iron Fireclay

Oxide	Analysis	Formula
CaO	0.20%	0.02
K2O	1.99%	0.11
MgO	0.50%	0.06
Na2O	0.20%	0.02
TiO2	1.20%	0.08
Al2O3	20.18%	1.00
SiO2	67.23%	5.65
Fe2O3	1.71%	0.05
LOI	6.78%	n/a
Oxide Weight		471.13
Formula Weight		505.40

Notes

A popular raw material for pottery clay bodies for many years. There is some confusion about the claimed physical properties of this material (the chemistry and firing absorption and shrinkage do not match with our own testing of the material). We found that by itself it has a drying shrinkage of more that 7%, which is a little too high for typical pottery clay bodies. We found it had excellent drying properties in spite of the high shrinkage (it scored A000 on the DFAC test). It had a 1% fired porosity at cone 6 and reached zero % around cone 7. It should be possible to make a pottery clay from Jordan fireclay as 100% of the mix and it should be serviceable around cone 5 to give some margin for error of over firing. However adding 25% kaolin should improve it somewhat, reducing shrinkage and increasing the maturing range to cone 6.

This material is known to contain natural feldspar fluxes, this resists the growth of cristobalite during firing, thus resisting shivering and thermal shock failure. Strangely, the chemistry from the manufacturer does not suggest this either.

Related Information

Jordan Fireclay fired test bars

Cone 6 to 10 oxidation (top to bottom) fired shrinkage and porosity testing bars.

Links

Materials	Fireclay
Typecodes	Clay Other Clays that are not kaolins, ball clays or bentonites. For example, stoneware clays are mixtures of all of the above plus quartz, feldspar, mica and other minerals. There are also many clays that have high plasticity like bentonite but are much different mineralogically.
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.

Data

Firing Shrinkage	Cone 1: 5.2% Cone 5: 6.7%
Frit Softening Point	3020F
Ultimate Particle Size Distribution	10 microns: 61.5% 5: 51.5% 2: 40% 1: 31.5% 0.5: 22.5%
Pyrometric Cone Equivalent	26-27
Water absorption	Cone 1: 6.6% Cone 5: 3.4%

By Tony Hansen
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