A fine-grained ball clay with excellent plasticity and strength. Old Mine #4 Ball Clay 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