Red Iron Oxide

Iron oxide (Fe2O3 in its red form) is the oldest and most widely used ceramic colorant, responsible for most of the earth-toned glazes in traditional pottery across every culture. Iron is abundant, inexpensive, and extraordinarily responsive to firing conditions.

In small amounts (0.5 to 2 percent), iron produces warm honey and amber tints in clear glazes. Around 2 to 4 percent in reduction firing yields the classic celadon green of Chinese and Korean traditions. At 6 to 10 percent, iron produces rich tenmoku browns and blacks, often with beautiful rust-colored breaks on edges. At 10 percent or more, iron saturates the glaze and can produce metallic surfaces, oil spots, or iron reds (depending on cooling).

Reduction firing (oxygen-starved atmosphere) is where iron truly shines. In reduction, iron shifts from its oxidized Fe3+ state to Fe2+, producing the greens and blue-greens of celadon. In oxidation, the same iron produces warm honey browns and tans.

Iron also affects glaze melt. It is a mild flux, so iron-rich glazes melt more fluidly than their colorless counterparts.

Typical usage: 0.5 to 2 percent for warm tints, 2 to 4 percent for celadon, 6 to 10 percent for tenmoku, 10 percent+ for saturated iron effects.