Kiln Cone Accuracy: Why Firing Temperature Matters for Glaze Safety
Kiln cone accuracy affects whether your glazes fire safely and correctly. Underfired glaze can trap raw material at the surface. This matters most for anything sold as food-safe. Getting your kiln’s real heat to match your target cone is a step many potters skip.
This guide covers what cone accuracy means. It covers why it affects glaze safety, and how to check that your kiln fires correctly.
What Kiln Cone Accuracy Actually Means
Cones bend at set heat levels. This mixes heat and time, not just one number. A kiln set to “cone 6” is aiming for that heat level, but the dial and the true heat inside can drift apart over years of use.
A worn part, a bad sensor, or a controller that’s off can all make a kiln show one number while doing something else inside. The gap is often small. But it’s the same small gap that decides if a glaze fully melts.
Why This Matters for Glaze Safety
Underfired glaze can leave the surface half-melted. On food-safe or daily-use pieces, that raises real concerns. A glaze that hasn’t fully melted may not seal the way it’s meant to.
This matters most if you sell mugs, plates, or other daily-use pottery. Buyers expect the glaze to work as it should. Checking that your kiln hits true heat every time protects both your work and the people who buy it.
How to Check Your Kiln’s Cone Accuracy
Set witness cones inside the kiln during a normal firing, where you can see them through a peephole. Compare how far each cone bends against the digital number your kiln shows for that same firing.
If the witness cone bends earlier or later than it should, your kiln’s real heat has drifted from its display. Run this check now and then, especially on an older kiln. Don’t just trust the panel to always match what’s really happening inside.
Kilns Built for Consistent, Accurate Firing
KMT 1027-3 Touchscreen
A touchscreen with set firing plans helps keep heat steady from firing to firing. This cuts down on the drift that older analog kilns often show.
KM 614-3 Pottery Kiln
Solid digital control at a lower price. Still built to hold true heat, firing after firing.
Simple Habits That Protect Firing Accuracy
Swap out elements before they fail completely, not after. Elements lose power slowly, and a kiln can still run while falling short of true heat.
Have your controller checked now and then, especially if witness cones keep bending earlier or later than they should. Small fixes now stop bigger problems later.
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