B Clay

High temperature, smooth, medium plastic, vitreous, buff-white firing, very clean illitic native stoneware.

Process Properties

B clay is probably our most balanced material. While it is suitable for stoneware production without any additives, in the interests of long-term body consistency this is not advisable. It is very smooth and slick and its plasticity is about right for a pottery wheel throwing body. This material is fine enough that a simple slaking process on the dry lumps will create a slurry of which +90% passes a 325 mesh screen.

From a workability point of view B clay is suitable as a major ingredient in stoneware clay bodies. Keep in mind that if non-plastics like feldspar and flint are added, you will have to counter these with high plastic materials like ball clay and bentonite to maintain workability.

Firing

Since B clay naturally vitreous at stoneware temperatures it is not necessary to add feldspar to flux it. This makes it possible to create bodies with higher clay content and better workability.

B clay has remained fairly stable for the period 1977-1996, although it has shifted somewhat in the degree to which it vitrifies at higher temperatures. Since 1990 minings have yielded a material that is more refractory than in the past (by approximately 2-3 cones). Thus more fluxes are needed for bodies employing this material and maturing below cone 9; less refractory materials are needed for bodies fired above cone 9. We recommend that you monitor the porosity and fired shrinkage of this material if it makes up a large proportion of your clay recipe.

Plainsman adds a small amount of barium carbonate to the standard retail product (about .5%) to precipitate natural soluble salts present in the material. This can be left out on custom orders.

Although B clay is very fine, it does not disperse or deflocculate. Soluble materials within the clay impede the action of normal deflocculants resulting in gelling of the slurry.

Glazing

Fired B clay is not difficult to fit stoneware glazes to, especially at higher temperatures. Its very fine grain and minimal impurities mean that it will present few problems with regard to glaze pinholing.

Physical Properties

Drying Shrinkage (+/- 0.5):
 1991: 5.7% @ 19% H2O
 1995: 5.8% @ 19%
 1999: 6.0% @ ?
 Dry Strength: n/a
 Water Content: n/a
 Drying Factor: C120-
 Dry Density: 2.0

Sieve Analysis (Tyler mesh):

     +48     (300 microns): 0-0.1%
   48-65 (300-210 microns): 0.0-0.3
  65-100 (210-149 microns): 0.7-1.3
 100-150 (149-106 microns): 1.5-2.0
 150-200  (106-75 microns): 5.5-6.5
 200-325   (75-45 microns): 9.0-12.0

Fired Shrinkage (+/- 0.5):

           1991   1995   1999
   Cone 6: 4.2%   5.0%   5.5%
   Cone 8: 4.8%   5.7%   5.8%
  Cone 10: 5.4%   6.0%   6.0%
 Cone 10R: 5.7%   6.1%   6.1%

Fired Absorption:

           1991   1995   1999
   Cone 6: 5.0%   2.5%   2.9%
   Cone 8: 3.5%   1.8%   1.4%
  Cone 10: 2.0%   1.0%   0.8%
 Cone 10R: 1.0%   0.5%   0.1%

Chemical Analysis

 BaO       0.4
 CaO       0.2
 K2O       2.2
 MgO       0.5
 Na2O      0.1
 TiO2      0.6
 Al2O3    15.6
 P2O5      0.0
 SiO2     72.7
 Fe2O3     1.2
 MnO       0.0
 LOI       6.5%

Plainsman Clays Ltd.
702 Wood Street, Medicine Hat, Alberta T1A 1E9
Phone: 403-527-8535 FAX: 403-527-7508
Email: plainsman@telus.net

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