The Clay Drying Process: Hints for Drying Pottery Evenly

Don't lose any more pots or sculptures thanks to these clay drying tips!

clay drying process - 1

Clay is a touchy material and it is important that potters understand the clay drying process to avoid problems. You can hardly blame clay for being fussy. It undergoes a lot of physical and chemical changes from wet clay to glazed, fired, and finished piece. 

Understanding the clay drying process is a great way to protect your work from future cracks and warping. As Snail Scott points out in today’s post, rushing the clay drying process is almost never good and care should always be taken to help pieces dry evenly. Read on for more great advice on drying pottery evenly and without incident. — Jennifer Poellot Harnetty, editor.


clay drying process - 2The clay drying process is, in many ways, more stressful to clay than the firing process. Uneven drying can lead to separation at small joints, and warped or cracked edges. While some clay bodies and forms are more vulnerable than others to these stresses, ensuring an even drying process before firing is always helpful.

The clay drying process – Plastic is your friend!

I’ve often thought that the greatest innovation in modern ceramics is not the electric kiln or powered wheel, but plastic. On pieces that take a long time to dry, a simple plastic cover assures both gradual drying and protection from uneven drying produced by exposure to drafts. But moisture from drying clay does have a tendency to condense inside the top of plastic coverings, often over-wetting delicate rims and details. It’s a good idea to place a layer of rags or paper towels between the clay and its plastic cover to trap condensation. Replacing these wet linings with dry ones regularly permits gradual drying and prevents exposure to drafts that cause uneven drying.

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For pieces that tolerate faster drying, you can omit the plastic entirely. Just make a “tent” of fabric or newsprint to keep out the unwelcome drafts and allow moisture to escape gradually.

clay drying process - 3Some ware made from forgiving clay bodies can often dry in the open air, if there aren’t any drafts to cause uneven drying or thin projections such as handles. These tend to dry first, since they are exposed to airflow on all sides. Long handles or similar structures with two points of attachment are especially vulnerable, since the clay at the two attachment points may dry at different rates, creating tension. This tension can lead to breakage either at the joint or on the handle itself. For these vulnerable pieces, wrap the fragile part in a scrap of plastic to slow its drying rate to match that of the rest of the piece. Or apply wax resist to these areas for a similar result, if you don’t mind the extra expense, production time and unwanted fumes during the bisque firing.

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Clay drying process – wrap edges!

Thinner and completely surrounded by air, edges are another vulnerable area where fast or uneven drying can cause warping and cracking. To protect thin edges, tear up plastic strips and place them on the rims of still-damp pots, slowing the drying process. Pottery with level rims can also be inverted to rest on its rim, effectively turning the whole piece into an edgeless closed form, though this can be hazardous for very delicate or not-quite-level rims.

clay drying process - 5Nothing is more frustrating than throwing your first bowl or forming your first teapot, only to see it break or warp during drying. It’s worth your time and trouble to protect your work while it dries to insure your
pottery making success.

So, remember:
1. When drying pottery, place a plastic cover over your pots.

2. Uneven drying causes tension that can crack handles and rims.

3. Dry pots upside down to even out the drying process.

4. Wrap handles and rims with plastic to help equalize drying.

**First published in 2008
Comments
  • Mike U.

    Hi from northern Japan. Since plastic is the latest scourge, why not use cardboard boxes to “cover” the pieces as they dry?

  • Robert S.

    When it comes to pinch pots the chances of getting cracks from differential drying are high. As I said above try a wet box. Make sure you wedge the clay really well before making coils or pinching as you want it all at same moisture content. Then put it in wet box for at least 3 days and then air dry to leather hard and trim. Never ever dry clay in sun as solar heat will dry it at different rates.

  • Robert S.

    I think one essential tip is missing. I use a wet box when I don’t have time to trim as this is a hobby for me. Get a large plastic sealing storage bin and pour two inches of pottery plaster in the bottom then let it cure. Once it does pour in water until the plaster stops absorbing it.

    When I put candles on or do any attachment I put the piece in the wet box which will result in the entire piece coming to the same moisture content overall couple of days. Then pull the piece out and let it air dry and then fire.

  • Shelly S.

    All basic info–and important. But we should all be looking for ways to use less flimsy disposable plastic (like plastic bags and dry cleaner bags) and more types of plastic that can be used over and over again before finally ending up in a landfill. I’ve been experimenting with using large plastic food containers turned upside down over clay pieces, and also a cheap indoor greenhouse–plastic, yes, but it’ll last much longer than many other options.

  • Louise O.

    We use dry cleaner plastic in the college continuing ed studio where i do my work. This is very light and doesn’t tend to mark wet clay but is large and flexible for a variety of work and can be reused indefinitely. It is also somewhat permeable so pieces still go through a slowed down drying process. I’ve had consistent good results by being patient and drying pieces very slowly over the course if several days, covering and uncovering to control the rate of drying.
    If I’ve been working on a piece that’s just at the right stage of leather hard and know i won’t be back for a while, I don’t want the work to get over-dry while I’m away. I’ll fold up a pad of a few sheets of newspaper and wet it at the sink – the surface ends up just damp while the inner layers absorb more moisture. I put the pad on a bat or ware board, place the piece, cover it with plastic and the damp paper maintains a gently humidified atmosphere until I can get back. Pieces are usually very close to the same state as when I left and I can pick up where I left off. It’s a useful way to extend the drying process to reduce stresses and uneven moisture content.
    This can also be used to restore moisture evenly to a piece that’s getting too dry to work but hasn’t gone entirely bone-dry. Depending on how far beyond the desired consistency it’s gotten, more paper that can hold more water, a more air-tight wrap and more time might be necessary to restore moisture content.

  • i did a little pot with a pinch base and coil top .clay was not leather hard, so cracks appeared.i want to know how to make the clay slab or a coil leather hard.pls help.me.any way i let my clay things under the hot sun to dry without knowing and they cracked.your tips for drying will be very important for my next attempt.thanks a lot!!!!!

  • i did a little pot with a pinch base and coil top .clay was not leather hard, so cracks appeared.i want to know how to make the clay slab or a coil leather hard.pls help.me.any way i let my clay things under the hot sun to dry without knowing and they cracked.your tips for drying will be very important for my next attempt.

  • Jeannelou T.

    Since i am ‘mother’s milk new’ to hand-forming, i can use all the tips i can get to avoid the natural mistakes. Thanks for the ‘hand up’.

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