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Published Feb 18, 2018

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Carpal Tunnel Syndrome is all too familiar to ceramic artists, especially those who work on the pottery wheel. But even those who don't use the wheel can run into stress and strain on their wrists from wedging pottery clay. So it is nice to hear about alternatives to the traditional wedging method. One such alternative is stack-and-slam wedging, a method that involves, basically, stacking clay pieces, slamming them down on the wedging table, cutting with a wire and repeating the process. This technique can also be used to work wet clay into clay that has dried out a bit too much.

Today,  Michael Wendt gives step-by-step instructions on how to effectively use this method for wedging clay. - Jennifer Poellot Harnetty, editor.


Wedging Pottery Clay (and saving your wrists!)

Stack-and-slam wire wedging is a method for wedging that is quick, effective, versatile, and easier on the hands and wrists than any other type of manual wedging. This method allows you to uniformly wedge very large pieces of clay for large pots.You also can add water (or softer clay) to pieces of clay that have become too stiff, or even mix clays with different characteristics such as stoneware and porcelain. In addition, this method offers a superior way to get perfectly flat slabs for tile work or handbuilding.

Two 3 pound lumps of clay. Clay after spiral wedging for 2 minutes. Stack-and-slam wedge 10 times: 1,024 layers. Stack-and-slam wedge 20 times: 1,048,576 layers. Stack-and-slam wedge 30 times: 1,073,741,824 layers.

To illustrate this method, I took two 3-pound balls of pottery clay of different colors and spiral wedged them for two minutes. I sliced through the ball to see how uniform the mixing had become. After two minutes of spiral wedging, there were still pockets of red and white clay in the pink mixture that had not been completely dispersed.I repeated the exercise with two more balls of different colored clays using the stack-and-slam wire-wedging technique. The bottom photos show the remarkable change that took place.


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The Stack and Slam Wedging Process

Choose a comfortable amount of clay for the first attempt. I seldom wedge less than 3 pounds because it is too slow to wedge each piece one at a time. I prefer to wedge enough clay for several pots at one time because, with this stack-and-slam wire-wedging technique, it is just as easy to wedge a large amount as it is to wedge a small amount.

First, block the clay into a rough rectangular shape. Next, lift the piece by the sides and cut it roughly in half on a wire. Pass the left arm under the wire as you place the two pieces back onto the wedging table. Make sure the cut is parallel to the front edge of the table. Take the piece closest to the table edge and carefully place on top of the other piece. Be sure not to make any dimples in either of the mating surfaces. Roll the joined pieces toward you, flipping them over so the bottom is now on top. Pick up the clay and slam it down with enough force that it ends up the original thickness you started with.

Repeat steps 1-3 at least 30 times. This will give you over a billion layers of clay particles! It is very critical that you pay attention to the lamination pattern since the final goal is to layer the clay rather than cross the layers with each other.

Once you have completed the required number of cycles, place your left hand on the top of the piece and roll it to the left onto its side. Now your right hand can be placed on the area that was the bottom on the table surface.

The goal is to keep track of these two surfaces while converting the block into a cylinder by repeatedly tapping it onto the table surface and finally rolling it round.

Taking this extra step assures you can keep track of the laminated face. I have found that orienting the laminations parallel to the wheel head minimizes cracks on the bottom of all of my pieces, and that selecting the smoothest end for the top further reduces losses.

Changing Softness of Clay

Sometimes clay is too hard for our liking. Water can easily be added with wire wedging resulting in the right feel every time. Slice the block first into thin sheets. Spread them onto the table surface and spray with water. Restack and wedge as explained or mix some softer clay with the harder clay. This lets you reclaim pots that have failed rather than drying them out and reusing them later. If some of your pugs are too hard and others are too soft, weigh out different proportions of stiff and soft clay. Record the amounts so that you can gauge how much needs to be added the next time.

Conclusion

If you're already happy with the results from your current wedging or pugging, there's no reason to change. But if you're struggling with uneven clay and would like a method that gives you more control, try wire wedging. It can create some troubles if done improperly -- most notably, the introduction of air pockets due to poor joining surface quality -- but this is easy to diagnose and cure. I have used this method for over thirty years and have no wrist or hand problems.

**First published in 2006
Topics: Pottery Clay