Apologies for the lack of posts lately; working silly-long hours at my day job at the moment (never have multiple clients in a crisis simultaneously) and also determined to stick to my “at least 20 hours/week” on my glass work.
At the moment I’m rediscovering my INability to add another six hours to the day, and thinking that sleep is truly a wonderful thing. Unfortunately, blog posting was one of the things I was going to do in that extra six hours I couldn’t magic up.
Nonetheless, I did promise to post additional pics of work done in Alicia Lomne’s wonderful pate de verre class at Bullseye last month, and a number of people wrote in asking for more info. (Read the first post about Alicia’s class)
I have a deeply ingrained aversion to revealing someone else’s techniques, especially if they make a living from them.
OTOH, Alicia is one of the most giving instructors I’ve ever met, with an almost missionary zeal to talk about pate de verre techniques to anyone who’ll listen, and we spent some time in class discussing online ways to do this.
Upshot: I wrote Alicia an e-mail telling her I’d mentioned her class on my blog and asking if she was comfortable with sharing more info about her methods. She said, “I am totally comfortable with you or anyone sharing information that I have given; I can not at this time respond personally to the requested information because of the short time I have at the computer.”
So, couple of things to note:
First of all, there’s a huge difference between me describing what we were taught and Alicia actually teaching it. Much of what Alicia teaches is a physical process that’s hard to describe without pictures–you really need to be there and feel how it works.
Second, I was so absorbed in the class that I didn’t do my usual shoot-every-process photography. Best I can do is talk about what I did in class. The actual process in the class is simple enough and in most ways follows classic French pate de verre methods:
- Make a solid clay model of the outside of the vessel you want to make and get it as smooth as possible
- Optionally, decorate the model with slightly raised or incised (about an eight-inch) designs. These will become inlays in a different color, that can be either ground level with the surface or left as-is for more texture.
- Secure the model, largest end down, on a flexible sheet of acrylic with a clay flange at the bottom.
- Invest the model with a “face” coat mixture of EPK (Edgar Plastic Kaolin, a type of clay powder), silica flour and potter’s plaster, to a depth of about an eighth of an inch
- Mix a second investment of silica flour, potter’s plaster and fiberglass shreds and cover the first (now mostly hardened) investment with a second layer to about a half inch. Level the top of the model (so the mold can stand upright in the kiln) with a section of sheet glass
- Once the investment has hardened (takes about 15-30 minutes), remove the mold from the acrylic sheet, take out the clay, and gently clean up the edges and make any corrections for bubbles or torn bits. Then gently schpritz the model with water–DO NOT SCRUB!!–until you’ve gotten the clay out and have a clean mold.
- Wrap the mold all the way to the lip with wet paper towels (the mold must be used wet for this method to really work well), then cover with plastic wrap to retard drying. Secure with waterproof tape.
At this point you have what looks like a lumpy bowl of wet paper towels with a plaster center, ready to be packed with glass.
And this is where it starts to get tricky–you’re going to mix frit (powder and fine, mostly) with water and gum arabic to form a sticky paste that almost holds together. Then you’ll spread a thin layer on the mold and tamp it in firmly to lock the particles against the mold walls. Repeat this process until you’ve evenly build up sufficient wall thickness, then fire the mold in the kiln.
We used a mixture of Bullseye fine and powdered frits, both transparent and opal glasses.* The powders can be sifted dry over the wet mold–it’s very difficult to pack them, so just let them drift onto the mold, where they’ll settle in and produce a lovely flocked-velvet surface.
You clean up any lines or edges of powder and frit with watercolor and lining brushes (which you can never again use for watercolor or lining). They do an excellent job of removing (not adding) powder, so that you’re literally drawing with the powder on the mold.
That’s the method I employed for the piece at the top of this post, which in that picture had just come out of the mold. Here you can see both the mold and the first layers of powders going down. I chose a combination of transparent greys and pale blues around the “face” gradually increasing the blues as I worked my way out to the edges. This first powder layer contributed most of the color to the piece; the subsequent layers simply darkened or brightened.
Once the powder was down, the mold was ready for the real work, i.e., packing three layers of frit into the mold and tamping it carefully (and firmly) down. Mixing fine and powdered frit gives a better pack, generally, and also let me play around with frit tinting, one of my favorite things to do with PdV.
(This is about the only time I use opaque colors in PdV; they can modify a clear or transparent (usually pale transparent) fine frit beautifully and give you an amazing range of translucent colors).
Alicia had us put the frit in a plastic container, schpritz in a little water, close the lid and shake like crazy to evenly distribute the water on the frit. Then we’d dump in powder (if we used any), shook it up a bit more, and finally add a few dollops of gum arabic. We shook again and mixed by hand to ensure that everything was well-mixed.
Now we had a sticky, thixotropic paste that would stay on the sides of the vessel, allow itself to be tamped very tightly, and dry like a rock.
In this shot (this is the first piece I tackled), I’ve laid in a mixture of BE Medium Amber powder and fine frit (with some additional tinting powder, mostly Marigold transparent and Yellow Transparent) into the bottom of the mold and tamped it down.
Then I started filling in the “inlays” with a mixture of BE Translucent White and BE White. (And no, I do NOT know the color numbers by heart).
Once I’d gotten the frit mixture packed to the top of the “inlays” in this piece (which took roughly forever), I began covering the entire bowl with a mix of BE Light Peach Cream powder mixed with fine Translucent White and Clear frit.
I kept the first thin layer fairly opaque, by the third packing layer I was mostly using Clear, trying to get some depth and translucency into it.
Alicia’s technique is mostly about the tamping–you do a lot more than you’d think. Alicia makes her own tamping tools or uses spoons. (Mine at home are primarily old drawer pulls on threaded rod and wax tools I snatched from my modeling stand).
The trick is to apply firm downward pressure for each tamping stroke, NOT a spreading or sideways motion. You want the glass to compact, not move against the mold, so you need tamping tools that can get into every nook and cranny in your mold.
Alicia at work sounds like a very fast typist or a percussionist playing a wood block. She tamps until the layer can’t be compacted any more, and you can actually hear the tone of the tamping change, becoming more and more drumlike. When she’s done, tapping the mold makes a tight, almost ringing tone at every part of the mold.
My layers laid down at about a quarter-inch, compacted to perhaps a third of that, and I build up three of them, plus the powder layer. The pack fills in the inlays so that the interior looks smooth, but should “ride” the larger contours so that the thickness stays relatively even. If you fill in every shape to level, you’ll wind up with radically different thicknesses at different points which can become too heavy and slide down during firing, creating a hole. (They also can become annealing headaches)
And, in fact, this was the principal difficulty with my first piece–there were so many deep inlays that I had to be very careful about compensating for thickness differences.
Learning to pack well takes practice and patience. Undercuts and switchbacks in the mold can be difficult to manage, and the mold dries out the glass can fall away from the sides.
The thickness stays pretty even throughout the piece, but Alicia puts in a slight taper as she approaches the top of the vessel. You can see how Alicia’s vessels thin out toward the top in the photo at right, a cross-section of a broken vessel. This photo also shows sifted dry powder decoration, shaped with a brush, on the outside of the vessel.
When packing was finished, I took the wrapping off the mold, cleaned the frit off the top of the vessel and neatened things up, and we stuck it in the kiln for firing.
Because the vessel walls are relatively thin the firing goes pretty fast (one thing I really like about this method–the thicker pate de verre packs that I do can take a week or more in the kiln).
I’m not going to share the entire range of schedules we used–this thing’s getting too long and I hate sharing schedules because kilns vary so much. But this is the schedule used for my first piece in the class, the cream and amber piece being packed in the above photos. (temperatures are in Farenheit):
- 600dph to 220 hold 2:00
- 250dph to 1100 hold 1:00
- 600dph to 1375 hold 30
- AFAP to 960 hold 2:00
- 50dph to 700 no hold
- 65dph to 500 no hold
- 100dph to room temp/OFF
|Seg.||Ramp (dph)||Temp||Hold (hrs)|
(or 900F/482C works too)
Note: When this was written, Bullseye had not yet offered a cooler alternative to their recommended 960F anneal soak temperature. Since then, they’ve suggested that 900F works equally well, so I’ve edited this to include both.
At home I’m modifying that to allow a little more drying time for the mold, slightly reducing the tendency to crack, and I’m playing around with process heatwork for different effects. At the low end, this is a very granular tack-fuse that resembles sugar. At the high end of heatwork, you get a translucent, waxy effect.
The exterior, next to the mold, will come away with a matte finish, sometimes with a tendency to scale (that’s easily removed with hand-padding). The interior will be glossy and–depending on your packing skill–a bit lumpy. If you fill the interior with talc you’ll get a matte finish on the interior as well.
The talc will also hold the glass to any questionable undercuts or switchbacks so there’s less chance the glass will fall away and make holes. I tend to use plaster of paris and sand mixes for this at home, but thanks to Alicia’s class I am going to experiment with using talc in my mixes. I probably should have used talc in the blue piece at top–I got considerable fall-away on the negative undercut I mentioned before–but I wanted to see just how far I could take Alicia’s methods.
Anyway, here’s the finished piece:
This is just out of the kiln, so there’s some scaling that needs to be removed, and I eventually finished this with diamond hand-pads, but leaving it as rough as I dared. I’d originally intended to grind off the top–the glass has a tendency to settle into “pricklies” at the top and generally needs to be ground if you want a smooth edge. In this case, though, I liked the effect so much that I decided to leave it–it complements the very organic texture in the rest of the piece.
I did have fall-away problems at the base; I probably packed just a little too tightly over the Medium Amber area and in the end left too little glass at the point where the base curves up into the bowl. As a result, I’ve got two little holes there. I decided not to refire to mend it; it’s a class piece and I kinda like it that way.
A number of us experimented with adding glass inclusions to the model; done properly, they embed into the investment, leaving one part exposed to the glass filling the mold. They’ll merge with the rest of the glass and provide very cool raised effects. I played around with a test tile using frit balls and came away with this:
The turquoise balls are solidly part of the piece, and they’ve preserved their shine and transparency, which is what I was looking for.
This is French Vanilla with Lt. Bronze shading for the tile, BTW.
I wasn’t that keen on the bronze shading, frankly; I thought it made the piece look a bit dirty instead of giving it the fine old patina I was hoping for.
I did my final vessel in French Vanilla and Turquoise, playing around with the color reaction. This, too needs a lot of top-grinding and hand-padding to finish it, but I think I’ll wind up with a nice piece.
That’s pretty much it (and apologies for the VERY long post). As I said, a lot of this is technique, and that’s best taught in class, or with a lot of practice. It takes patience, but it’s very much worth it.
*And, actually, that’s one are where Alicia and I diverge; I typically don’t use opaque frits except as colorants. Alicia, however, does it to wonderful effect.