Plywood Press Molds: A Great Technique for Enlivening Your Pottery Forms

plywoodmold_695

Potter Ann Ruel says that, although it was the mesmerizing spin of the potter’s wheel that originally drew her in to pottery, she soon felt she needed to break those circular boundaries. So she started altering her pieces into more complex forms.

Today, we present a technique Ann uses for making interestingly shaped press molds out of plywood. These slump and hump molds can create endless new possibilities for new forms for your pottery. – Jennifer Harnetty, editor.


Making a Plywood Press Mold for Pottery

To create asymmetrical pottery forms, I developed a stacked plywood
mold-making process to create slump and hump molds using a wood
construction technique I learned from Dewane Hughes at the University of Texas at Tyler.

The tools and supplies for this technique are available at any local home center
(or they may already be in your garage!).

  • 1/2 inch plywood (flat and not warped!)
  • Drill bit (wide enough for jigsaw blade to slide through)
  • Wood glue
  • Jigsaw with wood cutting blade
  • Masking tape, Utility knife
  • Angle Grinder (I use a 41/2 inch grinder) with sander conversion kit
  • Wood screws – 2 and 3 inch
  • Wood clamps (optional)
  • Painting canvas with a liner backing
  • Safety equipment (gloves, mask, ear protection, goggles, etc)
  • Handheld drill
  • Staple gun with 1/4 inch staple

Get more great project ideas in Studio Ceramics: Advanced Techniques – a compilation of techniques from a wide spectrum of experienced clay artists who have figured out something unique in ceramics, perfected it, and documented it so others could take it to the next level.


 

ruel_001

Figure 1

Creating Your Design

This mold design consists of layers of contoured plywood glued up in a stair-step fashion, which is then ground smooth. When designing and constructing the mold, work from the top layer down, keeping in mind that the mold remains open on the top and bottom. Sketch out some shapes that you want to use and cut out a template. The shape you settle on becomes the top rim of your finished vessel. For your first mold, create shapes that have wide sweeping curves and avoid tight curves because they’re hard to cut and sand.

Figure 2

Figure 2

Getting Started

Trace the shape onto a panel of plywood (figure 1) located so you have two to four inches of wood around the shape. The extra wood provides more gluing surface as well as rim support.

Drill a starter hole for the jigsaw blade close to the inside of the line you drew and then cut out the inside of the contour using the jigsaw (figure 2). Mark which side of the plywood is the “TOP” and label this sheet as “Layer #1.” Use a pencil or marker to make registration marks on the outside edges of the plywood rectangle so that when all the layers are finished, you’ll remember how to lay them together.

Figure 3

Figure 3

Creating More Layers

Place Layer #1 over the second layer of plywood and trace along the outside perimeter of the rectangle and the inside of your cut-out shape (figure 3). Take your ruler or compass and mark new measurements to the INSIDE of your traced shape (figure 4). There are no exact measurements. The specifications depend on the form you design.

Cut the second layer, remembering to label the plywood appropriately. After you’ve finished, stack the two sections together again and once they are properly aligned, extend the registration marks you drew on the edges of the first piece down onto the second one. These marks help you line everything up quickly when you’re assembling the whole thing to glue it together. Continue following this process until you have reached the bottom layer of your form.

Figure 4

Figure 4

Gluing the layers

Before you glue the sections together, do a dry run to make sure everything lines up. Arrange the layers, with the top being layer #1, down to the bottom in the order they were cut. Remember to keep an eye on the inside borders, making sure they are lined up the way you want them. They should appear as “stair steps” (figure 5). Don’t worry if they are not perfectly aligned, as you’ll eventually sand them flat. Apply a generous amount of wood glue in between the layers (figure 6). Use masking tape to hold the layers together so that they don’t slide out of place. Then, if you have wood clamps, use them to apply pressure to the stack so that a tight bond is formed or drive wood screws tightly into the corners of the stack.

Figure 5

Figure 5

Refining the Shape

Once the glue has dried, use the angle grinder to flatten the inside edges of your mold. To adapt the angle grinder for this purpose, you need to attach three things to the head of your grinder: the backing disc, gritted disc and the special nut using the illustrations from your Sander Conversion Kit. If you don’t have a grinder, you can use a Surform tool and a little elbow grease to get the contour.

SAFETY IN THE STUDIO!
When using the grinder or any power tool follow all manufacturer’s recommendations for safety including proper clothing and eye/ear protection.

Figure 6

Figure 6

Prop the edges of your mold off of your work surface using plywood scraps so that you don’t accidentally hit the table surface with the grinder. Slowly begin grinding down the stair steps so that your layers meld one into the next (figure 7). The grinder is a very aggressive tool and if you are new to using it, you may gouge into the surface. Don’t worry if this happens, you can always apply wood filler to smooth out those areas.

Figure 8

Figure 8

Finishing the Mold

Line the inside of the mold with painters canvas to cover up the wood texture (figure 8). The canvas also allows clay to easily release. Stretch the material tight and flat while stapling to the top and bottom of the mold. Cut darts in the canvas to help it conform to the edges.

Finished bowl

Finished bowl

Ann Ruel is a potter living in Chesapeake, VA. She’s a member of Ceramic Designers Association of Hampton Roads, and shows her work in galleries across Virginia.


**First published in April 2011

 

Comments
  • All these daily tips are great, but sometimes I wonder why I am paying to get my Ceramics Monthly and Pottery Illustrated, when this are the exact same articles that are in the magazines??

  • Cheaper, and EASIER by far, to do the same thing using styrofoam. Lighter too. We have these in the studio at Chandler Gilbert Community COllege, AZ. They have lasted under public use.

  • I create press molds by throwing, and altering, or handbuilding forms and then bisquing. These prove very durable and cheap as the cost of clay is the least of our costs.

  • Seems like a lot of work. I agree with others that it would be easier to make it out of clay and then just bisque it. Or pour plaster over the clay to make the mold.

  • I agree with Pat.. I love these, but then when I get my magazines I realize I have pretty much already read the articles already!

  • I guess some people are EXTREMELY process oriented. I’m not one of them so this seems like an awful lot of work when all of the above techniques probably work just as well. I use found objects when I want to make a drape or hump mold. I have also made one from plaster but think I’ll try the stryofoam approach. These would be so much easier to pick up and store.

  • My concern with styrofoam is that it has such a huge cost to the planet! So sometimes I will go for a more labour intensive process since you only make your mold once to create many pieces….just a view point.

  • Is there a post on how the foot / stand was made. I noticed the detailed embossing was wondering how that was made

  • This does seem like a lot of work, but probably produces a very tough long lasting mold. Seems like it would be good for complex shapes with details that wouldn’t holdup with plaster or styrofoam…or especially if you wanted a stairstep profile on the exterior of your piece. Coul be interesting.

  • I say this is great considering how clay warps when it dries etc. Looks to me like one of these forms is well suited for that. It is one of several ways to make a very nice work of art!

  • Barbara, you could also think of it as saving the Styrofoam from being discarded into the land fill bu reusing it from packing material rather than going out and buying new material. Taken care of, it should have a long life.

    Another thought on doing them out of plywood…most jig saws have an adjustable base where the blade will cut on an angle. In doing this you could save a lot of grinding and sanding time. Just a thought!

  • I agree with Craig, keeping discarded styrofoam out of the landfills from packing material has always been one of my big concerns. I have even gone to the dumpsters in shopping centers to look for it for a project. Right know I have too many styrofoam coolers, I receive refrigerated shots in them every month, they are stacking up in my basement. Any ideas what I could do with them, they are small some are approximately 16X12 others 12X12 small interior space. Thinking about donating them to a reuse it center if they will take them. Denice

  • Yes, I agree with Craig, angling the base would save a lot of time. Just remember to take more care going around corners and cut just inside the line so that the bottom one is not bigger than the top. I also thought of stepping the outside of the form for a different look. Another idea is to round the edges so you get concentric concave rings around the outside.

  • I’ve got some plaster cement that can be cast thin and hold up to something like 6 tons of pressure. It’s great stuff, I use it in this manner to make slump molds and it holds up great. I got away from no.1 pottery plaster because of it’s weakness. The only reason to use the plaster instead of clay is to get the negative of a piece instead of creating the negative out of clay. I like making the piece then casting the negative because it seems like I get what I want instead of just pretty close.

  • SYLVANA, What do you use to cut styrofoam? When I have tried to slice it I end up with a real mess. The edges are not sharp and clean and I am left with pilling.

  • I use a styrofoam cutting knife that I got from Hobby Lobby. It cuts with heat so it slices right through styrofoam and no pilling. I’d recommend using it outside though, styrofoam stinks when heated/burned.

  • I was cleaning out my storage area today and took a lot of white styrofoam to the daycare next door. The staff where very happy to take it and said the children would enjoy building with it. Styrofoam can’t be recycled in this city.

  • Hi, Styrofoam is very dangerous if inhaled. A real no-no to sand this or saw it if dust can be released into the air then inhaled. Also be aware of fumes if using hot cutter as this is also dangerous. I sound like my mother!
    Otherwise very nice idea. A bit labour intensive and a tad expensive for ply. If it is something to be used and used it may be more durable than plaster. I will try the idea of using bisque for this; thanks!

  • If you use styrofoam to make the mold how do you avoid the rough edges where the styrofoam is cut and or sanded?

  • This is a very interesting technique. I have done something similar that results in more free form piece. Stated very simply, I cut a hole in a 3/4 inch board. The hole can be round or oblong or a shape more along the lines of Ann’s mold. I then roll out, on a piece of light canvas, a suitably large piece of soft clay to give a generous overlap when laid on the board over the hole. Then, holding the board horizontal like a frame, I give each side of the board two or three taps against the top edge of my working table and the weight of the clay causes it to slump into a fairly organic shape. It then has to be left in the sling until it hardens up a bit so that it can be finished and made into whatever piece you have in mind. I get some interesting results that I find quite pleasing.

  • pour plaster over the styrofoam for a lighter weight, mold that can be used repeatedly. But I do like seeing how others work : )

  • Denice, I’ve got those styrofoam coolers from refrigerated meds, too… You can repurpose them as small damp boxes, to keep your unfinished greenware leatherhard. Pour a few inches of plaster into the cooler, and let harden for a day or two. When you need a damp box, just pour some water over the plaster and store your work in the cooler (put the cover on). The pieces should stay workable for a week or longer.

  • What a fantastic idea Terrill! That will save me wrapping up everything in plastic all the time. Thankyou!

  • I wonder why you would want to take out the steps! Leaving them in would make very interesting looking forms especailly if that was used as half of a container- though making the wood smooth for easy release and to avoid the grain lines would need a different technique.

    PS: Online is nice for quickie ideas- but, we get access to them in class, and the physical magazines are great for more permanent reference and so much more than just a technique manual to me!

  • I take old wooden picture frames from thrift stores (square, round, rectangular, oblong…) and add a bottom of plywood (if a piece is handy and the right size) or a couple of layers of heavy duty foam-core (left over from old framed 2-D art), cut to fit frame (wrapped with with heavy plastic sheeting (as moisture proofing) and duct-tape a loose liner of old T-shirt fabric.

    Very fast to make, and long-lasting (have used some for over 5 years in heavy use, classroom environment). Just have the students remove clay piece from form after clay sets up some, as opposed to leaving the item in mold to dry (can warp wood and cause fabric liner to mold/mildew/”rot.”)

    Works great. Students love them.

    I also make them from plaster (no liner), plastic/wooden/metal bowls and also make bisqued molds.

  • It’sa great idea for a durable mold. But, I am a potter, not a woodworker. Ihis project requires woodworking skills and tools I simply do not have, nor feel safe and comfortable using. I have NO skills to use:

    Jigsaw with wood cutting blade
    Angle Grinder (I use a 41/2 inch grinder) with sander conversion kit

    # Drill bit (wide enough for jigsaw blade to slide through)
    # Wood glue
    # Jigsaw with wood cutting blade
    # Masking tape, Utility knife
    # Angle Grinder (I use a 41/2 inch grinder) with sander conversion kit

    Plus requiring the added tools:
    Wood clamps (optional)
    Painting canvas with a liner backing
    ear protection, goggles
    Handheld drill
    Staple gun with 1/4 inch staple
    Handheld drill

  • this is just a silly project. There has to be at least a dozen ways to accomplish this with greater ease and results. Where in the heck would I put a monstrous mold like that? I make molds like this out of bisque and/or plaster. I have all the required tools to do this and figure this project would take a minimum of 4 hours to complete and then be big and bulky and really not function anywhere near as well as a bisque mold. Seems like simpler is quite often better

  • Ann is obviously a meticulous craftsperson. Her finished piece is something I would actually buy. Beautiful. I agree the mold technique looks laborious – but to each their own. I’m too impatient and would even use a plastic shape I like with cling film to release the work rather! And make a plaster or bisque mold of a favourite. Something of that careful process is transferred to the finished work though .. a sense of pride and old-world, unhurried workmanship in this world of ‘instant’ everything. Thanks for the post.

  • I normally used plaster of paris to make a mould for any shape. It is very easy and convenient as you can make the shape easily. Then you can press the clay into the mould evenly to form the article.

  • It is so fantastic the way artists can collaborate on these articles. I love ‘hearing’traded all the ideas and wisdom of experience. Recycling at its best. ~ k

  • gives me the confidence to use power tools…also wood is definately stronger and would last longer…nothing worse than your favourite plaster mold getting chipped…thankyou

  • I live in the same city as Ann and know her through the potters guild in the area. Her pieces are stunning.

    In answer to cutting styrofoam, I use an electric carving knife. Of course I don’t carve a turkey with it afterward.

  • To Denise and Terrill with the excess Styrofoam boxes: These make great hydroponic growing containers. Using them this way makes an environmental negative into a positive. Your local county extension office and Master Gardeners may be interested in a donation of superfluous boxes. Lettuces, for example, are delicious grown indoors this way since the plants are not stressed by weather and so do not become bitter.

  • I often wonder this as well. I also purchased numerous dvds and with time the vid’s show up on here as well.

  • If you choose to go the styrofoam route, do yourself a big favor and go to the hobby store (I got mine at Michael’s) and pick up a styrofoam cutter. This is nothing more than a stiff six inch nichrome wire that heats up when you turn it on. It cuts the styrofoam like butter and leaves a smooth edge. I can turn out new molds in 15 minutes. Do use the canvas to make removal easier and don’t forget to size your molds to provide for clay shrinkage and the thickness of the canvas.

    Happy mold making.

  • Thanks for your feedback! We do excerpt from our magazines, books, and videos, but usually do not post entire projects or videos. Typically we do two excerpts from each magazine per issue and a couple of excerpts from each book or video. So there is a lot more content in the products we sell. The sales of the paid products are what enable us to put the free stuff out there, so we really appreciate your support! Thank you!

  • I agree, but you can recycle existing foam packaging, giving it new life and keeping it out of the landfill.

Leave a Reply

You must be logged in to post a comment.

Enter Your Log In Credentials
This setting should only be used on your home or work computer.

Larger version of the image

Send this to a friend