Stack and Slam Wire Wedging: An Efficient and Easy-on-the-Wrists Way to Wedge Pottery Clay


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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 Harnetty, editor.

Wedging Pottery Clay (and saving your wrists!)

by Michael Wendt

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.
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Two 3 pound lumps of clay.

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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Clay after spiral wedging for 2 minutes.

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Stack-and-slam wedge 10 times: 1,024 layers.


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Stack-and-slam wedge 20 times: 1,048,576 layers.


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Stack-and-slam wedge 30 times: 1,073,741,824 layers.
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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.


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Next, lift the piece by the sides and cut it roughly in half on a wire.


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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.


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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.


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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.


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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.


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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.


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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 September 2006
Comments
  • I highly recommend this method. Think of it as a Dogwood sandwich that you have cut in half and then stacked to make even taller. You want the stacks to be parallel not perpendicular.

    I took three completely different clays, some muddy slip and went to work with this technique. I asked my spouse and child what 2 to the power of 30 was, they told me way too much to possibly get by cutting and layering clay so I demonstrated to them by not smashing the clay down and just doing 3 cuts which gave me 8 visible layers. I then got them to agree after smashing this tower down to a cutable size that when I cut and stacked it again I would have 16 layers and that it was clear that doing this 30 times would give me 2 to the 30th power layers (many millions). By the time I finished with my 30 cuts and stacks I had clay that was completely uniform and baby bottoms soft. It was far better mixed than anything I have ever done before and with far less effort. The hardest part was at the beginning when I had clay oozing everywhere and I must admit that I did use some spiral wedging then just to make it more managable. I did about 50 pounds (though I did divide it into two batches after the first couple of cuts). The only think you have to be careful about is that you don’t leave voids to trap in air bubbles but that is true with ram or spiral wedging as well.

  • What gauge wire should be used? I’ve tried to make this with a turnbuckle and attached to my wedging table and the wire keeps breaking!

  • I usually don’t knead or wedge any more since I have a Peter Pugger, but I do have a wedging table. I made it small, since I wanted it to tilt down (slightly) away from me for easier kneading. BTW, I’m calling the cut and slam method “wedging” and what most of us do I’m calling “kneading.”

    It would be great to have a portable wedging table, but I’m not sure how you would do that. It has to be either heavy or screwed down to something heavy. Otherwise, it jumps around as you work. I should have made mine heavier than I did. The top is a double layer of concrete board. You could do concrete–that would add to the weight. I’ve thought about filling the base with concrete.

    Michael Wendt’s description is great in that it brings up an important subject to potters, and will be a big help to anyone who tries wire wedging. That said, I couldn’t quite follow it, either. Plus, I’ve been taught that you want to mix up those layers and avoid lamination! (sigh) We all have our own way of doing things, and sometimes it makes a big difference what kind of clay you’re using as well.

    I start with a ball of clay (take as much as you think you’ll be able to handle, but remember that if you’re going to add wet clay, it will grow a lot. Cut it in half. Slam half down on the table with cut edge facing you. Slam second half on top of the first, again with cut edge facing you. Turn the clay 1/4 turn and repeat as necessary. Thirty times sounds about right to me. When you’re starting, it helps to slam down the clay in the non-dominant hand first. That way, when you’re aiming to land the second piece on top of the first, you’re using your dominant hand.

    If I’m adding moist or wet clay, I slam down the first half of my original clay, add a bit of moist clay on top of that, then slam down the second half. Watch out–you might get splashed if it’s really wet, sloppy clay. 😉 If the clay sticks to the table because of being too wet, a large putty knife can help you scrape it up. It’ll stop sticking once it gets mixed in better. Adding a bit at a time like this helps you to get the consistency you want. I usually wedge several times before adding more wet clay.

    When I first started doing clay, I was taught the ram’s head method of kneading, but I don’t like kneading this way. It does give you more chances to incorporate air. I use only spiral kneading (like a conch shell). It’s a little tricky to learn, but well worth it. I hope this helps someone. Wire wedging really is a lot easier than kneading and, I think, a lot more effective.

    Cindy

  • Jen, I’ve just been using the cheapy wire that came with my $4 beginners set. I hook one end over a hook that’s drilled into the wall, wrap the other end around the bottom end of my cane, hook my foot into the curved handle of the cane, and wedge sitting on a tall stool. If your wire is breaking my guess is that you’re overtightening that turnbuckle – it doesn’t take that much tension to do this.

    And I’ve found a video Mr. Wendt did demonstrating this technique. It’s on youtube at

    http://www.youtube.com/watch?v=HApNjUnI9U4

    I’m not sure why it’s not been linked to here but I found it very helpful to be able to see it done. The pictures included here are just too small for me to see the details of what’s going on. I learned to wedge this way many years ago; the other was called “kneading”. I had tried to recreate this technique last week and found I was mixing the clay really well but still ending up with fairly large air pockets. I think I was just futzing around too much with the clay between wire cuts. Now that I’ve had a chance to review the video I think I can do a much better job; I’ll be trying it out again tomorrow.

    If a picture is worth a thousand words, I guess sometimes a MOVING picture is worth a thousand thousand words, LOL!

  • Though it may sound (read) as if it is, this is is NOT complicated. Even I can do it! 🙂
    Not being quite as fussy as Michael, I simply cut the pug in half, slam down the left hand lump and then slam down the right hand lump on top of it. Pick it up and
    slice, slam, slam
    slice, slam, slam
    slice, slam, slam
    etc. Get a nice rhythm going. I also usually stop at about two dozen repetitions.
    For what it’s worth, for every 100 pots Michael takes off the wheel, typically more than 99 go on his shelves to sell. His failure rate is enviably low! He is very careful about every step of his work.
    The wire on my wedging table has a stiffish spring on the bottom end to protect the wire from breaking, and a turnbuckle attached on the upper end to an eye hook, so I can adjust the tension on the wire.
    Good potting!

  • For sculptors this is great for 6-8 lb. balls plus. If the directions are confusing try picturing the technique by repeating your hands with the steps in front of your screen. I am a tactile-visual learner and this is a piece of cake and a real time-saver!!

  • Re: “It would be great to have a portable wedging table, but I’m not sure how you would do that. It has to be either heavy or screwed down to something heavy. Otherwise, it jumps around as you work.”

    We have a portable board just for wiring the clay (we wedge on one of the studio work tables). The board is a simple construction of 2x4s and plywood with an angled cutting wire. It’s large enough to put a bag or two of clay on top to keep it in place. Problem solved!

  • I found Michael’s video and great explanation on Youtube titled Slam and Stack Wedging. Thank you very much. This requires much less muscle and is still doable for us old folks with issues. Ceramic Arts site is fabulous for beginners who want to learn.

  • Jen, thinking about your wire breaking – you may need to introduce some give into the system. You could do this with a small spring. You could probably salvage one from the bottom of an old baby crib, an old ironing board, or an old balance scale, just off the top of my head. Or you could make one – it’s not too hard, I used to do it all the time making jump rings when I was still silversmithing. Just google “making jump rings from coils” or similar. Basically all you need is a wooden dowel or short piece of round stock metal to use as a mandrel, a vise (to hold the mandrel), the wire you want to wind, and a pair of needle nose pliers to hold the wire as you wind it around the mandrel. There are ways to do the winding with a variable speed drill, but you need a way to stabilize the drill. Copper wire would be too soft; aluminum wire might be too brittle. Not sure about that. Not sure what gauge wire you should try either, but it’s not hard to wind a coil for such a simple purpose.

    Or you could try a short bungee cord – they’re cheap and easily available. You’d need one fairly stiff, but the short ones tend to be pretty tight as I recall. I’ll probably be giving a bungee cord a try in my makeshift setup – as I am working in a public studio I can’t have a permanent setup and my wedging would go faster if I weren’t expending part of my attention to trying to keep my foot hooked around the end of my cane, LOL!

    Anyway, adding a spring or some other way like a bungee to get some give in the system should solve your problem.

  • Love this method of wedging. I recycle my clay this way. Word of warning, make sure no one is around you. Air bubble’s have a tenancy to send clay flying every direction. I have added a shield around my board to catch most of the clay. I made a small transportable board that worked great and is not to heavy.

  • Great tips for a different way to wedge
    AND it’ll save my wrists! Wonderful!
    I love reading these tips from experienced
    potters. I’ll definately try it out.
    IMHO- I think a short video could make it
    easier to follow.
    Thanks

  • This is a great idea for discerning potters out there. However, if you are wedging in this manner simply to save your aching wrists, & with a single clay color, this can be simplified significantly. No particular order has to follow or number of times repeated; as long as you slam your clay firmly enough to eliminate air pockets, roll it, & repeat. Whether you use 3 slabs, two slabs, or nineteen; amd repeat 15, 25, or 90 times – in the end the results are the same if done consistently.

  • For a good portable wedging table, build a wood frame (any size) with a thin plywood bottom. Mix and fill the frame with potter’s plaster up to the level of the wood frame. Once it dries, it is perfect for wedging and works well to dry out clay that is too wet. Extend a short 2×4 piece of wood upright on one back edge. Then, attach a wire to it and bring the wire down to the front edge (along the same side) and attach it with an “eye” bolt or screw. Then, you have an angled wire for cutting your clay as you wedge.

  • I’ve been using this method for years and regularly use it to mix harder clay with softer clay. One of the advantages is that you can see when your mix is even because when you slam the stack down, if you look at the cut edge the softer clay protrudes more, giving an uneven surface. When it is ready and all the same consistency the surface remains smooth.

  • Ive used this method since I began. I’m not a great potter but I try.
    I constructed device that I wedge with and is portable anywhere. Its a 2×6 about 2 ft long. I cut the end to a 3 cornered point on one end. then I wrapped in it construction plastic. A clay bag, cut up will work. Staple it tight an the sides of the 2×6 so its smooth on the 2×6 surfaces. It leaves the point at the end uncovered. I used a wallboard screw and several washers to attach a string to the pointed end so it can go to either side. I tied a large washer to the end of the string as a grip. This works on up to 6# of clay, maybe more. One side can be used for darker clay and the other for light or white clay.

  • Sorry. Forgot to mention how to use the 2×6 wedger.
    Put it on a table in front of you. Place the string/wire down the middle on the 2×6 surface. Slam the clay, doesn’t have to be super hard, down on the string with your good hand. Whip the string up with the other hand. Pick the pieces up. Whack em together and repeat. Slam down on the string…etc.
    I found that for most clay the 20 repetitions works well. I always wedge so out of the bag, 10 or 15 works. Recycled clay is work no matter how you do it.

  • I watched the video and it was pure poetry. I am definitely going to wedge this way in future, especially as I have arthritis in my thumb joints. Thank you very much for the demo.

  • This is one of the best CAD posts ever! Extremely clear instructions AND a video to demonstrate -perfect!

    I have wedged using this method before and like how it is easier on the wrists. However, I am not sure I understood about the precise layering to get the best effect. Now, I know.

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