A unique high iron, slightly sandy, medium plasticity, refractory, deep red burning, native stoneware blend. Ideal as a source of iron in high fire iron red reduction bodies.

The raw clay before it is ground.

Firered is a blend of three high iron clays. About half of the mix is a refractory low plasticity bright red material mined in Manitoba. One third is a medium plastic maroon clay from Montana. The remainder is a bentonitic, pyritic brown clay from Saskatchewan. These materials complement each other very well and this mix is adjustable to deal with changes in any of the materials.

Firered is an excellent addition to high temperature clay bodies to darken their fired color for several reasons: First, it has typical plasticity and additions to a body will not upset the body's plasticity. Second, the refractory nature of Firered means that additions do not flux bodies the way iron-bearing earthenware materials do. Adding Firered to a typical buff stoneware, for example, will produce a classic variegated iron brown reduction stoneware. Third, Firered contains natural iron pyrite particles that impart attractive speckling in reduction firing.

Firered is the basis for the red colors of H440 and H440G and of the brown in H443.

FireRed thrown surface


These are six different runs of FireRed. The top bar on each is cone 10R, the next one down in 10 oxidation. The third one down is cone 8 (where the red color is holding).

Firered is one of the most unique stoneware materials in North America. It can be employed in bodies to produce very attractive deep red reduction effects. It is also ideal for use in dark colored refractory clay slips and surface treatments. In reduction at cone 10 Firered it fires almost black. In oxidation It has a linear progression of color change from cone 1 to 10, at the lower end it burns a homogeneous bright medium red, at higher temperatures it fires burgundy or deep red-brown. This is in contrast with many iron materials that are color-volatile (they darken in color suddenly at one narrow temperature range).

The achieve classic iron reduction variegation in bodies using this material it is necessary to tune their maturity so that they do not fully vitrify at the target temperature. Typically about 2% porosity or higher will give the attactive earthy warm coloration and texture. Thus it is best to warn your customers that ware made from such bodies should be used for non-functional purpose, or, if used for functional glazes should be fitted well and there should be a minimum of exposed unglazed clay.


The dominant contribution of Firered is fire speckle and dark iron color, especially in reduction firing. It works well with glazes that enhance the speckle and those that variegate in color according to thickness and how much iron difuses into the melt.

Physical Properties

 Drying Shrinkage: 5.5-6.5%
 Dry Strength: n/a
 Drying Factor: C130

Sieve Analysis (Tyler mesh):

     +48: 0.5-1.0%
   48-65: 2.0-4.0
  65-100: 3.0-5.0
 100-150: 4.0-6.0
 150-200: 5.0-7.0
 200-325: 6.0-8.0

Fired Shrinkage:

   Cone 6: 3.5-4.5
   Cone 8: 4.0-5.0
  Cone 10: 4.5-5.5
 Cone 10R: 4.0-5.0

Fired Absorption:

   Cone 6: 8.0-10.0
   Cone 8: 6.5-8.5
  Cone 10: 5.0-7.0
 Cone 10R: 2.0-3.0

Chemical Analysis

 BaO       0.3
 CaO       0.5
 K2O       1.1
 MgO       0.6
 Na2O      0.1
 TiO2      0.9
 Al2O3    15.4
 P2O5      0.2
 SiO2     66.3
 Fe2O3     6.9
 MnO       0.1
 LOI       7.6%

Safety Data Sheet

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Logo Plainsman Clays Ltd.
702 Wood Street, Medicine Hat, Alberta T1A 1E9
Phone: 403-527-8535 FAX:403-527-7508