Pocket glossary
Reduction
A kiln atmosphere lean on free oxygen. Potters use it as a lever on metal oxides—especially iron and copper—so the glaze’s final personality depends on timing as much as on recipe.
In everyday speech, “reduction” gets mistaken for a color mood board. In the workshop it is operational: fuel burns incompletely, carbon monoxide scavenges oxygen from metallic oxides in glaze and clay, and valence states shift. Iron that reads brown in oxidation can read blue-green in reduction—the heart of many celadon conversations. Our Longquan celadon essay walks through that chemistry without pretending every green glaze shares one mine.
Reduction is also a schedule: when you introduce it relative to peak temperature, how long you hold it, and how quickly you allow air back in during cooling all shift crystal growth and bubble escape. Electric kiln users sometimes chase “reduction” with localized sugar-smoke tricks or commercial pellets; those methods can color surfaces without reproducing the entire heat-work profile of a wood-fired climb. Honest writing names the equipment, not only the adjective.
Copper red as a sibling problem
Copper reds and certain iron greens are cousins under atmosphere control. A vase that “should” flash oxblood can end blotchy if oxygen sneaks in at the wrong minute. That sensitivity is why we link reduction to overglaze discussions only after the high-fire chapter closes: the second firing cannot rewrite the first atmosphere’s contract with the body.
Why the foot ring still matters
Atmosphere touches every surface, yet readers often meet vases through photographs of shoulders and lips. The foot ring—where the pot kissed the shelf—often preserves a different oxidation memory than the belly. Comparing those zones catches later refires and over-enthusiastic cleaning stories.
Overglaze is a different contract
Overglaze enamel is applied after a high fire has already fixed the main glaze. Its palette freedom comes at the cost of softer surfaces; reduction at the body stage does not “fix” that vulnerability later. Keeping those firing chapters separate saves beginners from one-sentence myths on forums.
Gas kilns, wood kilns, and electric kilns each make different bargains with reduction: flame path, damper culture, and programmer ramps are not interchangeable vocabulary even when the target atmosphere graph looks similar on paper. The East & Southeast Asian kilns atlas keeps returning to this point because export volumes amplified small workshop differences into global reputations.