Palestone

A fine grained, medium plastic, pale firing, native secondary stoneware clay that vitrifies from cone 8-10.

Palestone is a fine smooth plastic stoneware material mined in southern Saskatchewn. This material is very similar to our Midstone (which is a little less plastic and fires to a little lighter color). The two materials thus make an ideal blend to form the bulk of a stoneware body. Palestone is also available in raw lump form, please enquire.

Palestone is 'balanced' in the sense that it naturally contains feldspar and silica and can thus almost be used as a vitreous stoneware body with no additions. It is a high quality stoneware clay in that it is homogeneous and consistent over time. Many of our bodies, including M340, H550, H460 and L212 contain significant amounts of Palestone.

Process Properties

As is it is just a little more plastic than a typical throwing clay (unlike ball clays which are far more plastic). Bodies employing Palestone only need some less plastic filler material (or a less plastic clay) to achieve good drying properties. Thus, from a working properties point-of-view, Palestone is well balanced enough to be suitable as the main constituent for middle and high temperature bodies.

Palestone is actually a blend of native materials. It contains a small amount of ball clay that we can increase or decrease to compensate for changes in plasticity. It also has a small complement of a silty refractory clay to give us adjustability over drying properties and maturity.

Palestone contains small amounts of soluble calcium and magnesium sulphate materials that are hostile to the deflocculation process, thus it cannot easily be used in casting slips.

Since Palestone is a secondary sedimentary material, it is naturally very fine (even though it is ground to only 40 mesh, more than 95% will pass a 200 mesh screen).

Firing

Palestone is a true stoneware, very few such materials are available in North America. It burns to a vitreous grey-buff at cone 8-10 because it contains naturally occuring feldspar. It also burns very clean and speck free (unlike fireclays that often contain high levels of particulate impurities). Thus it is entirely feasible, even desirable, to make Palestone-based bodies that contain no added feldspar. In addition, Palestone is high in free silica, so bodies employing a significant amount may require no added silica and yet still fit glazes without crazing problems.

Physical Properties

 Drying Shrinkage: 6.5-7.5%
 Dry Strength: n/a
 Drying Factor: C130+
 Dry Density: n/a

Sieve Analysis (Tyler mesh):

   48-65: 0.1-0.3%
  65-100: 0.5-1.5
 100-150: 1.0-2.5
 150-200: 2.5-4.5
 200-325: 3.5-5.5

Fired Shrinkage:

  Cone 6: 3.0-4.0%
  Cone 7: 4.0-5.0
  Cone 8: 4.5-5.5
  Cone 9: 5.0-6.0
 Cone 10: 5.0-6.0

Fired Absorption:

  Cone 6: 5.0-7.5%
  Cone 7: 3.5-5.0
  Cone 8: 2.5-3.5
  Cone 9: 1.5-2.5
 Cone 10: 0.5-1.5

Chemical Analysis

 CaO       0.2
 K2O       2.2
 MgO       0.6
 Na2O      0.1
 TiO2      0.6
 Al2O3    18.5
 P2O5      0.0
 SiO2     68.6
 Fe2O3     1.4
 MnO       0.0
 LOI       7.7%

Plainsman Clays Ltd.
Box 1266, 702 Wood Street, Medicine Hat, Alberta T1A 7M9
Phone: 403-527-8535 FAX: 403-527-7508

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