Monday, August 19, 2013

August 11th Hint of the Week

Drying: Ceramic Arts DailySometimes, when I’m really on a roll in the studio, I find it difficult to be patient and let the work dictate the pace of the process. If it’s not ready to be trimmed, and I go ahead and trim it while it’s too soft, I pay the price in deformation or S-cracks after firing (from not compressing during trimming). The same can be true with drying. Rushing the process is almost never good. Luckily, it’s not difficult to dry your work evenly—assuming you can make yourself leave it alone. In today’s feature, Snail Scott walks us through the basics of drying and some simple ways to ensure success. — Sherman Hall, Ceramic Arts Daily

The 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.
Plastic Power
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.
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.
Some 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.
On 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.
Nothing 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 pots, 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.

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