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Pate de verre combines glass casting plus frit-painting plus sculpting plus moldmaking plus coldworking. Each of those can be daunting by itself; when you combine them, pate de verre can seem awfully difficult. In this project, I’m trying to reduce the complexity for beginners and still come out with an acceptable pate de verre piece.

Most pate de verre instructors start with a vessel; I chose a more forgiving form, the bas-relief panel. I began making these garden panels (above) because I needed fast, inexpensive pieces to sell at a show. I discovered, though, that they’re excellent student pieces. They require the simplest one-part box mold, (almost no) sculpting, and coldworking is kept to a minimum, so that the student can focus simply on designing the piece and packing the mold.

Besides, since the first pate de verre pieces were naturalistic bas-relief panels, there’s a nice historical symmetry to starting this way…

In Part I (this post), we’ll talk about making the model. In Part II, we’ll make the mold. In Part III, we’ll fill it, and in Part IV, we’ll finish it and discuss display methods.

My friends Shelby and Carla occasionally drop in for a “glass class day.” The idea is that I show them how to do something in glass, explain the concepts, and by the end of “class,” they have a finished piece and some new skills. They’re pretty informal, more like a quilting bee (except that I do most of the talking).

walterFor our last class, Carla wanted to make a pate de verre garden panel. The concept behind garden panels is simple, and harks back to the very first examples of pate de verre, developed by Henri Cros. Cros was attempting to rediscover techniques for ancient Egyptian faience, but with a modern, Art Nouveau sensibility.

The work that followed, by Cros and others, used natural themes. (I think) it reached its zenith with Amalric Walter and his partner Henri Berge, who created some of the most beautiful naturalistic pate de verre (right) ever made.

The garden panels follow that tradition and keep it pretty simple (in theory):

  1. Gather some weeds, bugs and seeds from your garden
  2. Embed them in clay
  3. Pour refractory plaster over the whole thing to make a mold
  4. Remove the clay, fill with glass and fire

It’s a leeetle more complicated in practice. The organic material may or may not be removed from the mold before the glass goes in. Whatever is left will burn out before the glass starts to soften. The voids fill with the packed glass, taking the shape of the now-vaporized plant part. Remove the fired piece from the mold, coldwork it and fire, and you have a nice little wall piece.

We chose to make panels that were about 5×7 inches, about the same as the ones in the slideshow at top. They’re maybe a half-inch thick, look nice on a wall, and teach some useful casting skills:

  • Choosing a good design for open-faced molds
  • Understanding how glass fills negative spaces
  • Engineering the model (and mold) to avoid casting issues
  • Making a simple box mold
  • Layering frit into a pate de verre mold
  • Simple coldworking and finishing

In this post, I’ll focus on making the model, i.e., the clay+plant components that the mold is built around.

Equipment and supplies needed to make the model

You’ll need clay tools and clay, plant (or insect) parts, and a few other things. Some you’ll around the house, some you can make. For the rest, make friends with your local ceramics supply house and glass stores, and shop their sales.

Important: Assemble ALL the tools needed for each task BEFORE you start.

Clay tools
Other tools
Supplies/consumables
Natural components for your model
About workspaces

 

Composing the panel (making your model)

gardenpanels-clayslabThese panels are made on a thick slab of clay. The clay acts both as the background for your plant material, and as the reservoir to hold the glass in the mold.

The fine and powdered frit we paint into the mold holds a surprising amount of air. When it softens and sinters into your mold, it can lose half of its original volume. So, even though the panel will only be a half-inch thick (or less), your mold walls will need to be at least a couple inches high to accommodate enough frit.

That means your clay slab needs to be at least 2-3 inches high.

1. Make the clay slab
Cut off a 2-3 inch thick section from your block of clay, set it on your palette and shape it into a block at least 2.5 inches thick.

You’ll probably trim your panel a bit, after it’s fired, so you’ll want to make your block’s footprint a little bit bigger than the desired finished size. If you want a true 5″ x 7″ panel, for example, you’ll want to make your block about 5.5″ x 7.5″ or so.

Tip: It’s a good idea to mark the slab unobtrusively, so that you know where the trim lines are. Otherwise, your composition may stray too close to the edge and be cut off in the finished piece. Unless the design is intended to “bleed” to the very edge, I find it best to keep my compositions at least 1/4 inch in from the trim edge.

Don’t worry about making a perfect block, but try to get it as flat and even as possible (above).

2. Choose components
Play around with the plants and pods you’ve collected; place them on the slab and rearrange until you come up with a pleasing design. A few tips:

  • gardenpanels-compositionSimple is better. One or three striking-looking seed pods may be more interesting than a vacant lot’s worth of weeds. Remember, too, that you will have to embed/support/trim/clean every one of those pieces, which can be time-consuming.
  • Try not to overlap. Lightweight components (as most will be) need to be embedded in the clay or they may float away in the refractory plaster. If you want to place a pod on top of a leaf, you’ll have to figure out how to get it to stay put.
  • Consider trimming thin/fragile parts. As with the wheat (above), a lot of thin, whiskery parts clumped together won’t show well and they may make the glass look flawed. Trimming off those areas can save cleanup time.
  • Remember the size of the piece. Most times, you’ll want the pieces to easily fit into the slab. Huge, thick pods, pinecones, etc., may look crowded.
  • Thin pieces may curl and tear. For your first pieces, it might be easier to stick with pods, cherries and other things that aren’t so fragile.
  • Take photos while you work. When you have a good arrangement, take a fast photo. It’ll save time later on, when you’re reassembling the piece. It also helps you remember what the original looked like when you’re filling the mold with glass.
garden-clayline

Half of this pod was embedded in the clay, so that the “draft” of the protruding part appeared to rise from the clay.

gardenpanels-pickingpartsYou’ll be embedding the parts in clay, so take some time to consider how you’ll embed.

A slight undercut at the base of a component creates a  shadow, giving the illusion of more depth. If the undercut is very severe, however, it can be difficult to remove the plant part without breaking the fragile mold. In that case, it might become impossible to remove the clay, and then it could become embedded in the glass.

It’s best to create a “positive draft,” in the mold, i.e., so that the part that sticks up from the background is widest at the bottom, becoming narrower as it increases in thickness (right).

gardenpanels-embeddingYou can also cut things in half if you’re running short of a particularly nice piece. Or you can cut slices for more interesting effects. Inside slices of a pinecone can be very beautiful (although they usually take a power saw to cut neatly).

Get in the habit of reviewing all angles of the piece for the best view. Spread the back leaves of trumpet-style flowers up flat on the clay, for example, and pull the front petals down (or cut them off) to reveal the stamens inside.

The undersides of leaves usually have stronger veining and details, so I often put the leaves face-down into the clay.

Arrange the plant parts on top of the clay, exactly as you’ll want them. Once you’re satisfied with your design, press them lightly into the clay, just enough to make an impression.

3. Embed your components in clay
garden-digholeforpodIt’s usually easiest to pick a direction and work consistently across the design. Start with the first piece, near the edge you’ve chosen. Set it aside and scoop a hole in the clay, right at the impression marks, to a depth of half its diameter.

Don’t worry about scooping out holes for stems and very thin components. But for everything else, you want to make a hole about the same depth as half of the component, just slightly smaller.

Press the component into the hole and gently pack the clay around it. You want it to look as if it grew naturally from the clay base. If you’re having trouble embedding both stem and pod into the clay, pull them apart.

Put the pods in first, then go back and carefully add stems later. You don’t have to embed the whole thing; you can cut pieces in half lengthwise. You’ll have less embedded in the clay, but you’ll get two for the price of one.

gardenpanels-placingcomponents4. Clean up your design
Once you have the general placement of components, it’s time to make them look natural. Plants don’t live only on a single plane; their stems can be twisted at compound angles, the leaves curl and bulge in places, etc., which can make it hard to get them to stay put in the clay.

Flattening and embedding every part of your design can make it look more like pressed flowers than natural art, and a stem barely tacked into the clay has the bad habit of floating away while you’re making the mold.

So…don’t even try. Let the stems and leaves spring up naturally, and then add/subtract clay to make them stable in that position.

If a stem is being pushed above the clay by a large bud, scoop out the clay and push the bud farther in, so that the stem lies flat. If a leaf or other thin component is too thin, put a little clay in the center, fold it over and seal it shut, then position as you need.

5. Engineer the model for glass

(click to enlarge) Once you've built your model, make sure the glass will have a clear path to all areas (and that you'll be able to dig out the clay).

(click to enlarge) Once you’ve built your model, make sure the glass will have a clear path to all areas (and that you’ll be able to dig out the clay).

Once you’ve got the composition right, you need to think “negative” and optimize your model for mold-making. It can be a difficult concept to grasp.

The model is the positive; it’s the area that will fill with glass to become the final piece. The airspace around the model, which will be filled with mold mix, is the negative. You’ll remove the positive (model) from the mold and fill the mirror-imaged negative space with glass.

Your mission as a mold engineer: Ensure that the glass can reach ALL parts of that negative space, and that you can get the clay out.

This is critical with any glass mold, but especially with pate de verre. You are carefully filling in each area with a specific color(s) of frit, so you MUST have access. Any clay left in the mold will bisque-fire and embed itself in the glass, ruining your piece.

So…examine your model and try to see where you could have problems. If there’s a very narrow, necked area as in the illustration (above, left), pack it with clay. Don’t pack all the way to the edge. If you leave a slight undercut you’ll still get a shadow line separating the piece from the background, but you’ll be able to reach everything easily.

bridgeNext, look for areas where the plant material sits above the clay, so that there’s airspace between the plant part and the clay background (right). Those “bridges” can trap plaster inside the glass, making it very difficult to remove in the finished piece. They might also be too narrow for the glass to reach easily, so that the void never fills.

Resolve them by building up a thin wall of clay underneath the bridge, so that there will be no plaster underneath. Make the top of the wall, directly under the plant part, just slightly thinner. That will retain the appearance of an undercut and make it look as if it rises higher than the background, even if it doesn’t.

Remember that any imperfections in the model will be reproduced in the mold and final piece. It’s a good idea to shine light on the model at different angles, to allow you to see dents and holes that you might otherwise miss.

If your plant parts have a lot of undercuts (like the chestnut pods I used), be very careful to clean the clay off every mold-facing surface, i.e., any part that might trap clay between the component and the mold. If you can’t get the clay out without breaking the plaster, it’s liable to become embedded in the glass.

Here are our models, in various stages of cleanup and engineering:

garden-carlas

Carla’s model: Iris leaves and lily-of-the-valley seed pods, on stems. In this shot, she’s built up clay behind the leaves to make them stand out, and is just starting to clean up and engineer the model for the mold.

garden-shelbys

Shelby’s model, which had a LOT of bridges and delicate parts to position. In some cases, she made the leaves stand out more by placing a small amount of clay in the center of the leaf and folding it in half.

garden-cynthias

My model: Chestnut seed pods and stems. The prickles on these pods won’t allow me to remove the pods from the mold (since I’d break the plaster). I’m being VERY careful to only allow clay on the undersides of the pods, where it won’t become trapped between the pod and the mold. If that happens, the clay will fire and become embedded in the glass, ruining the piece.

Since this is already hugely long, I’ll stop here. Next post: Making the molds.