Published Jun 15, 2022
The clay drying process is one of the most crucial parts of the ceramic process to get right. Not paying attention to the drying process can result in cracking or attachments popping off. In today's post, an excerpt from her book Mastering Hand Building, Sunshine Cobb gives some great tips on how to manage the clay drying process so that you avoid disasters! -Jennifer Poellot Harnetty, editor
How do you keep a piece from drying out while you work on it? In most studios, a simple, soft plastic sheet will be your primary tool (I recommend dry-cleaner plastic). The longer you leave a piece exposed to open air, rather than under plastic, the quicker it will dry.
Clay Drying Process: Environment
Besides the covering (or uncovering) of your work, the biggest factor in how fast your work dries is your studio environment. I have been lucky to live in places with a dry climate, so work tends to dry quickly and evenly if it’s not exposed to directional air (for example, an air conditioner or fan). What I love about a dry climate is you can work on multiple pieces simultaneously, easily moving from one to the next when each is ready. Still, it’s always possible for work to dry too fast.
If you live in a humid environment, work can take a while to dry. I have found that covering projects with plastic in high humidity can cause them to become completely saturated, absorbing atmospheric condensation and making pots seem damper than when you first wrapped them. Chances are you will still have to cover pieces when you leave them overnight, and you may need to return to the studio early to uncover them if you want to make progress on finishing them.
Clay Drying Process: Damp and Dry BoxesChances are if you’ve been in ceramics for a while, you have seen people use a propane torch or a heat gun to speed dry their in-progress pieces. Using a torch or heat gun can be very tempting, and each can be a great tool if used cautiously. I often use a torch in the early stages of a form, getting the foundation to firm up so I can continue building (1).
Here are a few best practices:
- Keep the object moving (preferably on a banding wheel) when applying heat.
- Be mindful about how close you allow the flame or heat gun to get to the form.
- Let the form rest a bit after you have heated it to let the moisture in the clay equalize (the water will migrate, and the clay will steam for a bit).
Here are things to avoid:
- Don’t heat clay that is prone to cracking or a form that is particularly thin.
- Don’t heat the surface where a future attachment is going to be made.
- Don’t heat a seam. It will start to pull apart.
- Don’t heat one spot too much. The goal is to dry your piece as evenly as possible.
- Don’t burn yourself! I prefer a propane torch with a trigger that, when released, shuts off the heat. Heat guns may seem safer; however, once they get hot, they stay hot in places. I have seen many people accidentally burn things they set too close to a hot heat gun or forget that the tool is still hot despite the absence of an open flame.
Clay Drying Process: Fast Drying Done Right
I’ve found one method of fast drying that seems to work better than just leaving a piece to survive in a dry room on its own. However, this requires having your own kiln or the permission of your studio technician or manager.
Place a sheet of dry-cleaner plastic over the piece, covering the form loosely but making sure to cover the whole piece from top to bottom and tuck the plastic under the piece securely. Vent the plastic bag at the top (dry-cleaner bags are perfect for this since most already have a hole for a hanger). Now either place the piece in a dry box or in a kiln set at 180°–200° F (82°–93° C) and hold for as many hours as necessary to dry the piece. (Don’t heat the piece to the point of boiling water, though, or your piece will explode.) Approximately one hour per half inch of wall thickness is the standard drying time or hold pattern I recommend. Note: This should be done only for work that is difficult to dry evenly or work that needs an extended drying period.
Photos: Tim Robinson.
Excerpted from Mastering Hand Building by Sunshine Cobb and published by Voyageur Press, an imprint of The Quarto Group. To learn more, visit www.quartoknows.com/books/9780760352731/Mastering-Hand-Building.html. The book is available for purchase from the Ceramic Arts Network Shop at https://mycan.ceramicartsnetwork.org/s/product-details?id=a1B3u000009udr1EAA.