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).
For 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):
- Gather some weeds, bugs and seeds from your garden
- Embed them in clay
- Pour refractory plaster over the whole thing to make a mold
- 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.
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As always, if you haven’t taken a class in safely working with the materials you’re going to be using AT LEAST READ THE MSDS for each of them. This isn’t a joke, folks; this stuff can give you silicosis, cancer, and probably the creeping heebie-jeebies, so do NOT mess around with it. There are some wonderful artist safety resources out there:
- Greg Rawls’ is an industrial safety engineer and also a great glass artist with a strong website on art safety. It’s a good place to start.
- Bullseye Glass publishes a good PDF on studio safety
- Monona Rossol’s The Artist’s Complete Health & Safety Guide is a must-have reference; it’s on Amazon in paperback and electronic form, and I keep mine on my iPad in the studio.
Respirator. For this project we know you’ll be working with refractory plaster, so a good “particulate respirator” is essential. Better known as a “face mask,” it prevents inhaling particles of plaster and any additives in the plaster. If you’re just starting out, a paper mask is fine, but look for a NIOSH rating of N95, and expect to pay a bit more for it than the cheap paper masks that come 3-5 to a pack. I stock a few for students, and they run around $20 each at the hardware store. (Look in the paint section)
If you plan on developing a glass casting practice, though, invest in a good-quality P-100 respirator. They’re not cheap, and you need to learn how to take care of one and regularly change its little filter cartridges. But they are far more comfortable than the paper masks–I don’t even think about wearing mine now–and they offer better protection. Mine is a half-face mask.
Gloves. Plaster’s also very drying to the hands; I know a lot of casters who mix with their bare hands but my hands would look like brillo pads in about 15 minutes if I did that. So I buy boxes of nitrile gloves from Costco, and use them religiously. One nice thing about them: When they’re covered with plaster and nasty goos, you just peel them off your hands, inside out, and all the goo stays inside the disposable glove.
Goggles. Goes without saying that you need eye protection whenever you’re in the studio, and it’s especially true when you’re working with plasters. They tend to float into the air and can land in your eye, making for a very uncomfortable and potentially nasty experience. If you wear glasses, great, but you’re going to scratch them up, so I’d wear an old pair, if I were you.
Cleanup. I know it sounds crazy, but there are artists out there who wear all kinds of safety gear while they work…and then clean up with no protection at all. You’ve probably got dust and all kinds of stuff floating all over your studio, and cleanup will definitely stir things up. The safety gear stays ON during cleanup.
Other stuff. I can’t imagine why you’d want to, but if you’re working with roofing tar paper, do NOT fire it in the kiln. It’s coated with petroleum products (tar), and if fired in the kiln will produce obnoxious and potentially toxic gases. You don’t need that, and neither do your neighbors.
Also, when you’re working with plants, seeds and other things found in nature, be a bit careful about how you collect and bring them inside. We’ve had some, er, interesting experiences with an angry displaced wasp.
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As clay projects go, this one is pretty simple: You’re making a block of clay, digging some shallow holes, and embedding stuff in it.
If you’ve already got an arsenal of clay tools, pull out some of these; they’ll come in handy.
- Scooping tools (as pictured, right) for scooping out tools. These come in wire or ribbon styles (the difference is the thickness of the cutting head–the ribbon removes more material), and they let you remove exactly the right amount of clay.
- Clay cutting wire (basically, a piece of wire wrapped around two wooden dowels). Clay cutters are cheap–you can make one yourself for about 50 cents–but are indispensable when you’re cutting a 25-lb block of clay into manageable chunks.
- Ribs/scrapers. These are thin sheet metal or wood cut into shapes, and they are wonderful for flattening and smoothing the surface of the clay. They’re inexpensive; you can cut your own out of roofing flashing or stiff plastic.
You’ll want a rectangular rib at least 3 inches wide, preferably 5. A rib that’s as wide as your clay will let you completely smooth the surface in one pass.
- Rolling pin. The best have ball bearings in the handles so they turn independently of the roller. I get mine from Goodwill for about $3, but an old dowel works, too. If you cover your rolling pin with a piece of old sheet (or get a rolling pin cover from the kitchen store), you’ll prevent the clay from sticking.
If you don’t have these, don’t worry; with the exception of the clay cutting wire, kitchen utensils can stand in for most of these tools.
If you’re a clay artist (or live with one) you know that the best clay tool is the one you haven’t bought (yet). While they’re not really needed for this project, if you’d like to do more with casting and sculpting, it’s not a bad idea to invest in good-quality clay cutting and shaping tools.
Clay-working tools are available at most hobby and art supplies shops, but you’ll get a better deal (and selection) if you shop at a local ceramic supply place. If there’s not one near you, try an online ceramics supply, but until you know how you like to work, that’s a chancy proposition.
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There’s not much, really.
- Camera. I take (as you can probably tell) LOTS of process shots. They’re extremely useful when you’ve filled a mold and can’t quite remember what went where. I typically take shots of:
- The “layup,” i.e., the arrangement of plant parts on the mold before I start embedding, to help me remember what goes where
- The finished model
- The model prepped for mold-making (which gives me a guide to what went where when I’m filling the mold)
- The finished mold once the clay is removed
- The frits I’ll be using (a photo is faster than writing everything down)
- Interesting stages in filling
- Mold placement in the kiln (with a board showing the firing schedule I’ll be using)
Taking so many pictures has been a lifesaver on several projects. The camera doesn’t have to be fancy (in fact, a fancy camera isn’t a great idea, given all the messes in the studio). I often use my smartphone, but I also have a cheap digital just for the studio.
Dry cleaning bag. If you need to leave your clay for more than an hour or so, wrap it in a dry cleaning bag. If you don’t have one, saran wrap or a plastic garbage bag work equally well.
- Palette. A palette (also called a batt) isn’t really needed for this project, but can be useful. I typically sculpt clay on a flexible palette of 1/4-inch acrylic, covered with a piece of old bed sheet or flannel.The fabric keeps the clay from sticking, and it’s easily removed when it’s time to make the mold. The plastic flexes just enough to make it easy to detach the mold. I buy my palettes at the local plastics store, from their scrap bin.
- Turntable. Every part of this project can benefit from a turntable, probably one of the most useful non-glass items you can have in the studio. It allows you to reach all parts of the work without stretching or brushing a sleeve over something fragile.My favorite come from TAP Plastics for about $7, but ceramic turntables, lazy susans, or a couple of boards attached to a raceway from the hardware store work equally well. I prefer the transparent versions, because I work on a light table and don’t want the turntable stopping light transmission.
- Ruler. For measuring clay, etc.
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- Clay. For each panel you’ll want need 6-7 pounds of the cheapest earthen (water-based) clay you can find, or a slab that’s about 5″ x 7″ x 2-5 to 4″ or so. This time, we used a Dick Blick clay, “Wonder White.” It doesn’t really matter if it has “grog” in it or not; personally, I prefer grog-less because it’s easier on my hands.
- Water. It’s a good idea to keep a squirt bottle of clean water around, and a largish bowl of water, too. The squirt bottle will help prevent the clay from drying out, and the bowl of water is where you’ll clean your tools.
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This part’s easy: Head for your yard, or the nearest weedy vacant lot, or open your refrigerator, and see what’s available. If you can fit it in your hand (and it doesn’t bite), it’s a candidate for a garden panel.
In 15 minutes in my backyard, Carla, Shelby and I accumulated a LOT of potential material (right). We gathered a lot more than we could actually use, to give us room to play with compositions. We looked for things with interesting shapes or details, that were relatively thick and not too fussy.
You can also head down to the hobby or florist’s shop, and pick up some dried flowers and pods (left). The stems and floppier parts of dried flowers are sometimes reinforced with metal or plastic, and will need to be removed before you start. (They’ll make a mess in the glass)
Fruit or veggies that are starting to go bad can make wonderful molds. We grabbed some blueberries from the bushes in the backyard (but wound up eating them instead) and some about-to-mold bing cherries from the fruit bowl.
BTW, you don’t have to confine your attentions to the plant world. I’ve seen people cast fish, chicken feet, large insects and worms, dried-up frogs and bird skeletons, etc. Just remember that whatever you put in the mold either must come out BEFORE you fire…or must burn out completely, which can be incredibly stinky.
Warning: Just because it’s natural doesn’t mean it’s totally free of inorganic material. Skeletons, for example, contain a lot of calcium that can remain in the mold, and some plants may contain grains of silica. They can be gorgeous in some circumstances, but for our purposes they’re gonna gunk up the glass.
If you’re firing something like that, you’ll need to either open the kiln and remove all the gunk around 500-700F, or plan on a dual firing. More about that in another post.
How to choose
Since these would be Carla and Shelby’s first panels, we wanted to keep things easy by choosing plant parts between about 1/8 inch to 3/4 inch thick. That size won’t complicate schedule calculations, and it make molds that have sharp, easy-to-see-the-fill-lines areas. Nobody chose anything thicker, but if they had wanted to use pine-cones or thick seed pods/fruit, we could have cut them down with a power saw.
We tried to find leaves that were thickish and stiff. They usually stand up best to handling, and don’t dry out quite as fast. And they also tend to have the most visible veining and details.
Tip: Frequently the undersides of leaves are better candidates than the tops, since they have the most extreme veining.
Very fine detail, such as slender long stalks, fine pine needles or blowzy dandelion heads, can be absolutely stunning…but could take some serious mold engineering to get right. Try to avoid them until you’re comfortable with mold-making and cleaning.
When tendrils are too thin, they’ll simply disappear into the mold material and won’t be captured at all. Or they can make a “bridge” over the plaster that flowed underneath it, trapping plaster in the glass.
Wheat stalks make beautiful panels, but their whiskery things will usually disappear into the plaster. What you’ll be left with is the hard, interwoven kernel of wheat. (left)
Shelby chose a trailing vine of thin, ruffly leaves for her piece, a challenging choice for a first piece but the heart shape of the leaves was inspiring. Carla found some lily of the valley seed pods and long, ribby iris leaves that were just about perfect.
I dug out some old chestnut pods I’d picked off the ground in front of my office last year; they’d dried out and split, but were still attached to the stems. They’re thick and woody, not something I’d recommend for a first attempt, since they’re virtually impossible to pull out of the mold.
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Where to work
Clay and mold mix are pretty messy, so this isn’t a kitchen project. If you don’t have a specific sculpting and moldmaking area already, take the project outside or do it in the garage. If that’s not possible, cover your work table (and if possible, your floor).
If I’m teaching or demonstrating, I ask the venue to put down drop cloths.
CAUTION: NEVER EVER EVER EVER EVER put refractory mold mix or clay down a sink unless you’ve installed a special trap to catch the waste (and even then, don’t do it on purpose). This stuff can accumulate in pipes and cause blockages in very expensive places. If you think you’ll be doing this a lot, consider adding something like a Gleco trap to the ONE sink you will use for your projects.
For those of us who don’t have Gleco traps or similar on our plumbing, the two-bucket method works best:
- Fill two 5-10 gallon buckets about halfway full of clean water.
- As you finish using a bucket or tools, drop in the the first bucket (the “dirty” bucket) and give it a good scrubbing
- When it looks clean, rinse it in the second bucket (the “clean” bucket)
- When the dirty bucket is TOO dirty, set it aside, and start using the clean bucket (now the dirty bucket). Fill a new “clean” bucket with water.
- Leave the used-up dirty bucket out in the sun. The water will evaporate, leaving a cake of dried plaster/clay/whatever that you can throw out.
You’ll want to cover your work surface to protect it. I use kitchen or grill aluminum foil, the widest roll I can find. It provides a smooth surface that doesn’t stick, withstands heat, and at the end of a session can be rolled up and tossed out, mess and all.
I find it easier to work on a large table, sitting down, with a smaller table beside me for tools and such. That way I don’t constantly look under my sculpture for a missing wire tool.
Good light is essential. If you’re outside on a warm summer day, as we were, great. Otherwise, multiple clamp lights with good overhead light let you easily find problems in the clay–the better the light, the faster you’ll resolve problems.
Composing the panel (making your model)
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:
- Simple 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.
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).
You 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
It’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.
4. 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
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.
Next, 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: