Woodfire Clay

This is a non-vitreous, high temperature, plastic, buff burning lightly grogged body specially formulated to flash. In general wood firing is done to achieve an effect called "flashing" (one common example of flashing is an orange/red/brown coloration on the unglazed body surface). The type of flashing achieved is a product of many factors, some of which are not well understood. However potters that have achieved good flashing generally agree that it is related to firing method and body formulation. Our Woodfire body has been demonstrated to flash well in our tests. However woodfiring methods, philosophies and body preferences vary greatly in the woodfire community and we recommend you test this material in your circumstances before buying a large quantity. If you have developed a knowledge of the mechanisms of flashing and would like to help we would be happy to share our recipe and entertain your suggestions.

Ten percent grog has been added to add texture, prevent warping, and improve drying. Early runs of the body employed silica sand as the grog (a common practice in woodfire bodies). However we have switched to a fired kaolin grog to reduce abrasion during modelling and throwing and reduce dunting cracks during firing cooldown.

Throwing properties are excellent even when quite soft. Even though it contains a considerable amount of grog it feels smooth (except against the wheelhead when throwing). It has a throwing character similar to a Lincoln Fireclay body, very pleasant to work with. Since this body is quite plastic we recommend care in drying (even though it contains grog).

Firing

Wood firing

We have formulated this body to be a little less vitreous than a typical cone 10 stoneware (since wood fire kilns are often fired past cone 10) and recommend its use in the cone 10-11 range. Since it is high in silica, firing below cone 10 will result in less maturity and dunting could occur if the kiln is cooled too quickly. Some isolated iron speckles will occur in reduction firing, these are from the grog material.

Physical Properties

 Drying Shrinkage: 6.5-7.0%
      Dry Density: n/a

Sieve Analysis (Tyler mesh):

   35-48: 5.0-8.0%
   48-65: 4.5-7.5
  65-100: 3.0-5.0
 100-150: 5.0-7.0
 150-200: 5.0-6.0
 200-325: 6.0-7.0

Fired Shrinkage:

  Cone 8: 5.0-6.0%
 Cone 10: 5.5-6.5
 Cone 11: 5.5-6.5

Fired Absorption:

  Cone 8: 4.0-5.0%
 Cone 10: 3.0-3.5
 Cone 11: 2.5-3.5

Chemical Analysis

 CaO       0.3
 K2O       0.3
 MgO       0.3
 Na2O      0.0
 TiO2      1.1
 Al2O3    30.6
 P2O5      0.0
 SiO2     59.5
 Fe2O3     0.7
 MnO       0.0
 LOI       7.1%

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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