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OM #4 Ball Clay

Alternate Names: OM4 Ball Clay, OM4, OM#4, OM 4, Old Mine #4, OM-4 Ball Clay

Description: Tennessee Ball Clay

Oxide Analysis Formula
CaO 0.20% 0.01
K2O 1.10% 0.05
MgO 0.50% 0.05
Na2O 0.20% 0.01
TiO2 2.00% 0.10
Al2O3 26.30% 1.00
SiO2 59.70% 3.85
Fe2O3 1.30% 0.03
LOI 9.30%n/a
Oxide Weight 354.09
Formula Weight 390.40


Old Mine #4, Mayfield, KY.
A fine-grained ball clay with excellent plasticity and strength. Old Mine #4 is an "industry standard" based on its popularity in both casting and plastic formed bodies. It is also widely used as a suspension aid in glazes.

OM#4 ball clay is variable in nature and tends to be more vitreous than some of the more refractory ball clays that are available. It has some soluble salts which can give a brown coloration to the surface, so barium carbonate may be needed to precipitate these.

Physical Properties
Water of Plasticity: 32.8%
% Dry Shrinkage: 6.2
Dry M.O.R. (50:50 ball clay:silica, psi): 610
pH: 4.0
M.B.I. (meq/100g): 9.2
Specific Surface Area (sq-metre/g): 23.1
Soluble sulphur SO4: Low

P.C.E.: 32

Particle Size, Microns: 20 10 5 2 1 0.5
(% finer than) 96% 91% 83% 68% 57% 46%

Fired Properties
Cone 5 10
Total Shrinkage: 11.3% 13.6%
Absorption: 11.1% 4.2%

Shipped from Mayfield, KY

*This info is from a data sheet from Jan 2013

Related Information

OM4 Ball clay fired from cone 10R (top), 10 down to 4 (downward)

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Ball clays are normally refractory, none of these are vitrified to any extent. The cone 10R bar is yellow because it is stained by the soluble salts present in the material. These are very typical of what most ball clays look like.


Typecodes Ball Clay
Ball clays are abundant and very plastic and are used in all types of plastic forming bodies. They are not as white-burning or refractory as kaolins but lower in iron and fluxes than bentonites.
Materials Gleason Ball Clay


Pyrometric Cone Equivalent 31
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