When to Reduce and for How Long
In a gas kiln, reduction is not applied from start to finish. The firing schedule has specific windows where reduction is introduced:
- Body reduction: Applied around cone 010–09 (early in the firing, when the clay is still porous). This affects the clay body itself, pulling iron into the surface and creating the characteristic warm or grey tones associated with reduction stoneware.
- Glaze reduction: Applied during the last stages before peak temperature, roughly cone 9–10. This is when metal oxides in the glaze are most reactive and reduction has the greatest effect on glaze colour.
Neutral and Light Reduction
Not all reduction is dramatic. Many potters use light reduction: just enough to shift colours slightly without the heavy, smoky results of deep reduction. The skill is in reading the kiln and adjusting the flame accordingly.
Electric vs. Gas: A Philosophical Choice
Electric and gas kilns produce genuinely different aesthetic results, and neither is better. Many potters work exclusively in electric oxidation their entire careers. Others are drawn to the unpredictable, organic quality of reduction work.
If you are starting out on an electric kiln, you have access to the full range of commercial glazes and very consistent results. As you advance, exploring a gas kiln (even through community studio firings) can be a transformative experience.
Pro Tip: Reading the Kiln
You can tell a gas kiln is in reduction by looking at the peep hole. In reduction, a soft orange or yellow flame "lick" will be visible coming out of the hole; the kiln is slightly pressurised and flame is escaping because the combustion is incomplete. A clear, invisible exhaust means you are in oxidation. Learning to read this visual cue is one of the first practical skills you develop firing a gas kiln.
Simple Reduction Log
For each gas firing, jot down:
- When you started body reduction (cone reading/time)
- When you shifted to glaze reduction
- Visual notes from peep holes and resulting colors
Over a few firings, this becomes your personal atmosphere playbook.
The clay remembers the fire it went through. That story is part of what makes every pot unique.
Keep Exploring
The tradition of reduction-fired stoneware was championed in the West by potters like Bernard Leach, who studied under Japanese masters and brought gas kiln reduction techniques to British studio pottery. The philosophical appreciation of fire-marked surfaces connects to the Japanese concept of wabi-sabi, which values the beauty of imperfection and natural process.
Common Mistakes and Quick Fixes
- Reducing too early or too heavily: Use cone windows and gradual adjustments.
- No peep-hole observation habit: Watch flame behavior and log what you see.
- Changing body and glaze reduction together: Adjust one phase at a time for clear learning.
- Assuming unpredictability means no control: Consistent logging turns reduction into a repeatable craft.
Practice Exercise
Create a three-firing atmosphere journal: note body reduction start, glaze reduction start, peep-hole flame behavior, and final colors. By firing three, patterns emerge and your choices become intentional.
