Drying Clay Before Bisque Firing: Pottery Basics

Drying clay all the way through before firing prevents cracks, breakage, and wasted glaze. Here’s why it matters, what can go wrong, and what you can do to mitigate damage.

Why Let Clay Air Dry?

Avoiding cracks and explosions
If there is any moisture left inside the clay, it turns to steam as the kiln heats up. Steam needs somewhere to go, and if it is trapped, it will force its way out. This can crack or even shatter your piece.

Better structure during firing
Clay that is dried well is less likely to slump, warp, or fall apart in the kiln. It holds its shape better and survives the firing process with fewer surprises.

Even shrinkage and fewer problems
When clay dries evenly, it shrinks evenly too. This helps prevent warping and cracking, and gives you more predictable results when firing.

Faster, easier firing
Fully dry clay fires faster and uses less energy because the kiln does not have to work as hard to drive off extra moisture.

Glaze sticks better
If clay is even a little bit damp, glaze can go on patchy or flake off. Dry clay helps the glaze go on smoothly and stay put.

How to Dry Clay Properly

Go slow and steady
Cover your piece with plastic or a drop cloth to slow down drying. Plastic grocery bags work well for small things, while dry cleaning bags are good for larger pieces. Make sure the cover has no holes over important areas.

Balance the exposure
If one area dries faster, like the rim of a bowl, adjust your cover to even things out. Cut a small hole over the thicker section, or wrap handles and attachments to slow them down. The goal is even moisture loss.

Check with your hand
If the clay feels cool to the touch, it is not ready yet. The cool you’re feeling is moisture in the clay. Thick pieces need more time. Make sure the inside dries just as much as the outside.

Try a damp box
A damp box is a great way to control drying speed, especially if your studio air is dry. You can make your own or buy one. The Clay Plant makes a good one, based on Danny Meisinger’s method.

Porcelain vs. Stoneware: What’s Different?

Different clays dry at different rates. Knowing how your clay behaves can help you avoid problems.

Porcelain
Porcelain has finer particles and dries faster on the surface. Because it has less plasticity, the outside can dry and shrink before the inside catches up. This is why porcelain is so prone to cracking. Slower, even drying is key. In winter, a humidifier can help. I let my covered porcelain dry as slowly as possible and find that extra humidity really helps prevent cracks.

Stoneware
Stoneware usually has grog or sand mixed in, which adds strength and lets moisture escape more evenly. It is less likely to crack and is more forgiving than porcelain. Still, thick pieces need extra time and attention.

Bottom line: Porcelain needs slow, careful drying to prevent cracks. Stoneware is a little easier, but you still need to pay attention, especially with larger or thicker work.

How to Tell Greenware from Bisqueware

When you are working on several pieces at once, it is easy to get them mixed up. Here is how to tell if your clay has been fired yet.

Greenware (not fired yet)
Color is close to the original clay, just lighter
Still fragile and easy to scratch or dent
Sounds dull when tapped with metal
Softens if it gets wet

Bisqueware (fired once)
Color is lighter or more muted
Surface feels harder and does not scratch as easily
Rings when tapped with a pin tool or other metal tool
Does not soften in water, but still absorbs it, so do not soak before glazing

Knowing the difference keeps you on track and helps you avoid glaze mishaps. If something cracks after glaze firing, you can always try a Kintsugi repair, but ideally, you want to avoid cracks in the first place.

Using a Long Preheat Cycle in the Kiln

If you’re programming your own kiln for a bisque firing, adding a long preheat at a low temperature helps remove leftover moisture. This is useful for thick pieces or when you are not completely sure your clay is bone dry.

If your piece is nearly dry but you’re not fully confident, and it’s not extra thick, you can do a 12-hour preheat at 200 degrees Fahrenheit to finish drying. This is low risk for most work (but use your judgment). Preheating is not a replacement for careful air drying, but it can help in a pinch.

Slow and Steady Wins

Getting your clay bone dry before firing is not just a good idea, it is essential. It keeps your work in one piece, saves glaze, and cuts down on wasted effort later. Taking your time here sets you up for better results every time.

Thanks for reading and happy firing.

❤︎ C

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