Firing pots in a gas kiln in a reduction atmosphere (lack of oxygen) is always interesting as you never know until you open the door, what the exact results will be.
If there is copper in the glaze, it can turn bright red instead of green. If there is iron in the glaze it can come out a lovely chestnut colour.
And that is what happened today. The stacking bowls Gerry made for me are just want I wanted, a rich brown tenmoku, and the jugs for a customer have come out red.