Mid temperature off-white porcelainous stoneware. Contains more than 60% ball clay, 21% PV clay (a plastic feldspar), 6% talc and 10% fine silica sand. This is a mid-temperature stoneware, firing off-white with almost no speckling, combining porcelain-like glaze effects with strong working properties of stoneware.

Fired at cone 6

Process Properties

F97 feels very smooth on throwing (even though it contains a significant amount of fine silica sand). As a high ball clay body, it generates slip very well and has superior throwing characteristics even when comparatively soft. F97 will appeal to people who like a 'slick' responsive feel with a little tactile feedback.


Fired bars are a nice dense grey buff cone 7-9. Below that they are buff coloured. At cone 8 the silica sand imposes a texture on the fired surface.

Because F97 contains significant silica sand we recommend that you exercise care when firing it through quartz inversion.

Fired bars from cone 8 (top) to cone 4 (bottom).

Thermal Expansion

We do not supply a thermal expansion value. The reason is that such numbers often mislead users. First, a body has different thermal expansion characteristics when fired at different temperatures, schedules and atmospheres. Dilatometers are only useful when manufacturers can measure bodies and glazes over time and in the same firing conditions. If a chart is supplied here, please view only as a way to compare one body with another.

Another significant issue is that many customers compare measured thermal expansion numbers with calculated values of glazes in efforts to fits those glazes to a body. This does not work. Calculated values are relative only and have limitations that must be understood. The best way to fit glazes to your clay bodies is by testing, evaluation, adjustment and retesting. For example, if a glaze crazes, adjust its recipe to bring the expansion down (using your account at insight-live), fire a glazed piece and thermal stress it (using an IWCT test, 300F into ice-water). If it still crazes, repeat the process.

If we recommend a base clear or glossy glaze, try calculating the expansion of that as a rough guide to know whether your glazes will fit.

Physical Properties

 Drying Shrinkage: 4.5-5.5%
 Dry Strength: n/a
 Drying Factor: A000-B110
 Dry Density: 1.95

Sieve Analysis (Tyler mesh):

     +48     (300 microns): 0.0-0.6%
   48-65 (300-210 microns): 0.4-0.8
  65-100 (210-149 microns): 2.5-3.5
 100-150 (149-106 microns): 2.0-3.0
 150-200  (106-75 microns): 5.5-7.5
 200-325   (75-45 microns): 7.0-10.0

Fired Shrinkage:

   Cone 4: 4.5-5.5%
   Cone 6: 5.5-6.5
   Cone 7: 6.0-7.0
   Cone 8: 6.0-7.0

Fired Absorption:

   Cone 4: 6-8%
   Cone 6: 2.5-3.5
   Cone 7: 1.5-2.5
   Cone 8: 1-2
Logo Plainsman Clays Ltd.
702 Wood Street, Medicine Hat, Alberta T1A 1E9
Phone: 403-527-8535 FAX:403-527-7508
Email: plainsman@telus.net