A fine grained, medium plastic, red firing, native material that vitrifies around cone 7. Suitable as a plasticity-neutral ingredient in medium and high temperature red and brown burning bodies.

Process Properties

Redstone is balanced enough that it can be used as-is for many applications requiring deep natural color. Any intermediate color or maturity can be predicted and created by blending Redstone with Midstone and Palestone. Any mix of the three will make a workable body.

Note that Redstone contains enough soluble materials that are hostile to the deflocculation process that it cannot easily be used in casting slips.


A typical set of fired bars. We can compare runs, see color progression and measure porosity/fired shrinkage over a range of temperatures using them (cone 4 (top) to 8).

Redstone burns to an attractive red at cone 4. By cone 6 it has darkened to a deep red. By cone 8 it is blistering and beginning to expand toward melting. At cone 2 it fires a warm red progressing down to a typical terra cotta color at cone 02-04. Redstone is somewhat more resistant to bloating than our other materials and overfired ware tends to soften and warp before bloating occurs.

Redstone is thus ideal as an iron source in low and medium bodies. It is much cleaner to work with than iron oxide:buff clay mixes and its color change is linear across the cone 1 to 5 range.

Some customers are using it as a terra cotta material in preference to Redearth because red color development is excellent and it does not have as volatile a response to overfiring. In addition it dries a little better and has less soluble salts.


Redstone is not been fine ground like most industrial minerals. While this offers process properties advantages, it also means that if bodies containing it are fired quickly or with stiff-melt glazes pinholes could occur.

Physical Properties

 Drying Shrinkage: 6.0-7.0%
 Dry Strength: n/a
 Drying Factor: c331
 Dry Density: 2.0

Sieve Analysis (Tyler mesh):

     +48: 0-0.1%
   48-65: 0.2-0.8
  65-100: 1.5-3.5
 100-150: 3.0-5.0
 150-200: 2.0-5.0
 200-325: 5.0-9.0

Fired Shrinkage:

 Cone 2: 3.5-4.5%
 Cone 4: 4.5-5.5
 Cone 6: 5.0-6.0  higher
 Cone 8: 3.5-4.5 (bloating)

Fired Absorption:

 Cone 2: 5.0-7.0%
 Cone 4: 3.5-4.5
 Cone 6: 1.5-2.5

Chemical Analysis

 BaO       0.4
 CaO       0.3
 K2O       2.6
 MgO       0.9
 Na2O      0.1
 TiO2      0.7
 Al2O3    14.6
 P2O5      0.3
 SiO2     68.5
 Fe2O3     5.1
 MnO       0.0
 LOI       6.5%

Safety Data Sheet

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702 Wood Street, Medicine Hat, Alberta T1A 1E9
Phone: 403-527-8535 FAX:403-527-7508