A2 Ball Clay
Description
A smooth and highly plastic, buff burning, refractory, coarse grained, lignitic ball clay. A2 is mined in Southern Saskatchewn and is both a ball clay and a fireclay. We have large reserves of this material and it is consistent from mining to mining. Ball clays are suitable in a wide range of ceramic and non-ceramic applications. When A2 is fine ground (which we do not currently do) it is very similar to commercial ball clays from the southern USA (although a more plastic and a little more refractory).
While kaolin is white and clean and considered pure clay mineral, ball clays, by comparison, are generally grey or brownish in color and differ in the following ways:
- They have a much finer ultimate particle size
- They contain organic material, especially lignite, that darken the raw color
- They are much more plastic and suspend better
- They contain chemical impurities that darken fired color (especially iron oxide)
- They melt at a lower temperature.
- Ultra-fine particle size: Ultimate particles can be 0.2 microns
- Flat-shaped aluminum-silicate particles of high resistance to heat and acid attack
- Affinity for water: The particles have a surface chemistry that attracts water and holds onto it
- Surface area: Only bentonite and similar minerals have a higher surface area than ball clays
- Very high plasticity: They are suitable as binders, suspenders, plasticizers.
Plainsman A2 has been actively mined it since the 1970s. While having the same general properties as other commercially available products (e.g. those from the southeastern US), this has several advantages:
- Lower shipping costs for the western and northwestern part of the continent
- We can produce at coarser particle sizes
- We can custom-blend ball clays with other clays from our quarries to create custom materials
- Plainsman has very responsive customer service, sales and technical support departments
- Plainsman can deliver a consistent product quickly.
Process Properties
As a ball clay, thus it improves plasticity of any body recipe to which it is added. However it will also increase drying shrinkage, slow down drying time and increase the difficulty of drying ware without cracking.
A2 contains some soluble salts. These are hostile to the deflocculation process so this material is not suitable in casting body recipes.
Although A2 powder looks like many other ball clays, it is not fine-ground to 200 mesh (the largest particles in the standard 42 mesh size call be felt). For ceramic applications it is thus not suitable in porcelains for whitewares. However in native stonewares it contributes and earth and natural look to the fired surface.
Other applications: We can produce custom mesh sizes and package A2 in bulk bags for non-ceramic applications (please call).
Firing
A2 has significant iron content so it does not fire white. The soluble salts in A2 will produce a flashing effect during firing in reduction, turning the cream colored surface to brownish. Since we only grind the standard material to 42 mesh, A2 will bring fired speckle to reduction bodies (these are ironstone concretion particles that fuse in reduction atmospheres).
Physical Properties
Drying Shrinkage (50:50 calcine:raw mix): 5.5-6.5% Drying Factor (50:50 calcine:raw mix): C130 Dry Density (50:50 calcine:raw mix): 1.80
Sieve Analysis (Tyler mesh):
35-48: 0.1-0.4% 48-65: 1.0-3.5 65-100: 1.5-5.5 100-150: 1.0-4.0 150-200: 3.0-7.0 200-325: 5.0-9.0
Fired Shrinkage (50:50 calcine:raw mix):
Cone 6: 4.0-5.0% Cone 8: 4.5-5.5 Cone 10: 5.5-6.5 Cone 11: 5.5-6.5
Fired Absorption: (50:50 calcine:raw mix)
Cone 6: 11.0-15.0% Cone 8: 9.0-11.0 Cone 10: 7.0-9.0 Cone 11: 6.0-8.0
