IROXR
Ferric oxide, milled fine — even colour rather than specks · Amber in oxidation; celadon greens and blues in reduction · More of it gives tenmoku browns and blacks; a saturated addition gives iron reds · Stiffens a melt in oxidation, thins one in reduction
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Red iron oxide is ferric oxide, ground fine enough to give an even colour rather than specks. What it gives depends on how much goes in and on the kiln atmosphere.
Red iron oxide gives amber and tan in oxidation from a small addition, and the celadon greens and blues in reduction. More of it takes the colour through olive to the browns and blacks of a tenmoku. A saturated addition gives the iron reds, which want oxidation and go maroon or black if the kiln reduces hard. Iron is also a flux, but only sometimes: as ferric oxide it stiffens a melt, and reduction converts it to the ferrous form, which thins one. That is why the same glaze can run down the pot in reduction and sit still in oxidation. Specks come from granular iron rather than from this, which is milled too fine to speck.
