Redstone

A fine grained, medium plastic, deep 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.

Redstone is balanced enough that it can be used as-is for many applications requiring deep natural color. Intermediate colors can be 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 be used in casting slips.

Redstone fired bars

Redstone burns to an attractive red at cone 4. By cone 6 it has darkened to a deep red (and overfired). By cone 7 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 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 quite linear across the cone 1 to 5 range. For use in cone 6 bodies the base body recipe should mature around cone 8 (this will flux it down to cone 6).

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.

 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
 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

 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%