We all end up with clay scraps when making pottery, and because this happens at various stages in the cycle, we need a way to bring all of that clay to an even level of moisture and consistency so it can be used again. But there is no one way that works for everyone in every studio.
So in today's post, an excerpt from our second edition of our free download, Successful Tips for Buying and Using Pottery Clay, we present an assortment of simple tips for recycling clay without a lot of equipment or hassle. - Jennifer Harnetty, editor.
The work we make generates discarded clay scraps from trimming and slop from throwing or handbuilding. Whether you make your own or buy prepared clay, you need to decide what to do with used clay. For some, the solution is to throw the scraps in the dumpster and dump the slop down the drain, which isn't really a solution. It's economically and environmentally wasteful and can wreak havoc on your plumbing, sewer and septic systems.
All discarded clay‚ except that which comes in contact with plaster or other contaminants‚ all is recyclable and reusable. Reclaiming it requires planning a system for your particular studio situation. Although there is no one way that works for everyone, some basic guidelines can make this job easier.
Collecting and Storing
A trash container of some sort is the key to any system. Placed on wheels, it can be maneuvered anywhere in your studio. Remember that when filled with clay scrap, slop and trimmings, it will be very heavy, so buy a heavy-duty container, and use heavy-duty casters for the dollie. Pouring the scrap clay through a framed screen that sits on top of the container breaks up the scraps into smaller pieces and catches tools that got lost (see above).
When you are done with a day's work, dump your throwing slop and any scraps into the bucket. If you plan to recycle scraps that have fallen on the floor around your wheel, make sure there's no non-clay debris on the floor first, otherwise you should simply throw these scraps away as the foreign matter could cause problems. Rather than using a broom, use a metal dustpan and your hands to collect the clay.
As the bucket approaches the top, decant the water. As long as there is water over the layer of clay in your recycle bucket, the clay scraps will all break down and become thoroughly saturated. If there are lumps or dry material in the slop, the resulting reclaim will have hard and soft spots. You don't have to mix the clay in the bucket with a mixer. Let the water do its job.
Learn more about the clays, glazes, materials, and supplies you use in your studio in Richard Zakin's Electric Kiln Ceramics: A Guide to Clays and Glazes.
The resulting very wet scrap usually needs to be dried out before reprocessing can continue. Here‚'s a list of the more commonly mentioned and used methods.
Spread a thin layer (2-inches or so thick at most) of scrap onto an absorbent surface (figure 2). Plaster bats, wedging tables and large plaster slabs are good choices for this. A material called HardiBacker Board works very well. This is a heavy cement board that is not as effective as plaster, but is strong and will absorb moisture from the clay. Caution: do not use sheetrock. This is thin and porous, absorbs water very quickly, then the paper delaminates from the surface and the boards weaken. Flip the clay slab over periodically (it should pull away from the surface easily when it is ready to flip) and continue to do this until it is right for wedging.
Store drying bats on a vertical rack or ware cart to save space. Note: the HardiBacker boards need a board underneath for support. Some potters prefer to dry their reclaim outdoors. Note: cover the reclaim with a sheet or other breathable fabric if you live in a windy area to prevent foreign materials from getting in your clay. A fan can also help dry wet clay more quickly. This will accelerate the drying, so turn the clay frequently.
Another practical method involves a rudimentary filter press system made from cotton pillowcases. Simply fill the sacks with clay slop and hang them up, either over a bucket or outside. Excess water eventually drips out over time and evaporates from the surface.
Jonathan Kaplan is a frequent contributor to Pottery Making Illustrated. He has been actively involved in the ceramics field for 40 years. He lives in Denver, Colorado, where he curates Plinth Gallery.
For more of this article and some great information on selecting and purchasing the right clay for your needs, be sure to download your free copy of Successful Tips for Buying and Using Pottery Clay: How to Select, Process, and Test Clay Bodies for Better Results.