Fire-Red is an unusual material for several reasons. It has a high iron content yet is a fireclay (the iron percentage is so high that it fires black at cone 10R). It is also non-plastic. Most important, it is not ground to 200 mesh like industrial materials. This body demonstrates it well: 42.5% Fire-Red, 42.5% ball clay and 15% feldspar. All that ball clay gives it awesome plasticity. The feldspar gives control of the degree of vitrification (just raise or lower it for more or less). This recipe produces good density and strength yet still exhibits deep red color! Look closely at the surface: It is covered by thousands of tiny iron eruptions, these will bleed through an over glaze to give "speck-city" like no other!
Fire-Red Data Sheet
A sought-after visual effect that occurs in reduction fired stoneware. Particles of iron pyrite that occur naturally in the clay melt and blossom up through the glaze