The sculpture that wouldn't die

Part III: Filling the mold and firing

>>>>The sculpture that wouldn’t die, part II (of 3)


In Part I, I wandered through a lot of creative angst and a clay sculpture I called “Triangle.” Now, in part II, I pretty much wreck the whole thing in seven deadly mistakes.

coveredmoonpendantUsually I make a silicone master of my clay sculptures, to ensure I can reproduce the piece if disaster strikes. Once I have the master, I can pour as many waxes of it as I like, modifying each wax for whatever I need. (One of my jewelry pieces, right) is actually a fragment from a much larger piece, Currents, that I showed in the previous post)

But silicones are an expensive, time-consuming pain. I can spend more than $100 on a silicone master and it adds at least 24 hours to the process. Then it takes almost as much time to pour and refine the wax and prep it for investing as it does to make the original sculpture. Plus, the wax must be steamed out of the mold, a finicky task that adds even more cost and time. And with every step you add, you increase the risk that you’ll ruin the piece and have to start over.

Worst of all, all that moldmaking kills the spontaneity of sculpting, which is what I love most. As vital as silicones are, they tend to turn sculpting from a joy to a chore.

I already had silicones of the faces, the important parts, and my entire being (including my wallet) rebelled at doing yet another batch. So I just poured investment over the clay, dug it out and left it at that. (that was mistake #1)


Then I went into my usual colorpanic. I rarely get through any sculpture without second-guessing myself on glass color. While I pondered (for three weeks), I left the mold on the edge of my worktable. (mistake #2)

One day I whacked the drying mold with a 25-pound bag of clay. Crrrrrrrrraaaaaaack. And I’d hadn’t made a silicone mastermold. Dammit.

A top left section of the mold broke off. Fortunately, it was in a no-detail area. I glued it together with more plaster, some cement and reinforcing strips, added a cradle layer of heavily strengthened plaster/silica to the outside of the mold. Thought about pouring a very soft silicone positive directly into the mold, then using that to… naaaaah. The mold looked GOOD–why waste silicone? (mistake #3)

I finally chose a warm-neutral palette with “antiquing.” (If you sift a layer of contrasting-colored powder into a pate de verre mold before doing your REAL colors, the contrast powder will sift into the crevices, giving you lovely highlights and shadows that resemble antiquing in paint.)

I re-dampened the mold, sifted and started tamping in glass powders and frits. It took a little more than 12 hours to pack that mold–lots of detail needing individual coloring–so I didn’t finish until after 2AM. Normally I’d have gone to bed and started the firing the next day, but I had only a narrow firing window for Triangle. To stay on schedule it had to go to the kiln NOW, so exhausted or not, I carried it carefully to the kiln. (mistake #4)

I generally build feet on my pate de verre molds; feet get the mold up off the kiln floor, allowing air to circulate, and make it easier to level the mold. Several readers, though, have asked why I don’t just level my molds in a sandbed like everyone else?

Since my backup investment “cradle” had reduced the feet, I decided to try the sandbed route, even though I hadn’t done it before (mistake #5). Then I thought that, if I built it up a bit more, the sandbed would also help keep the mold together, in case that whack had cracked more than just the part of the mold I repaired.

That required more sand, which kept sliding down onto the shelf. It was nearly 3AM, I was tired and grumpy and I didn’t want to mess with it anymore, so I finally built walls of firebrick to keep the sand in place, poured in the sand, and set the mold inside. (mistake #6)


I could call this one a comedy of errors, I suppose–the first Triangle, inside its unfortunate heat baffle in the kiln. BTW, the hot pink areas are the Bullseye kilnwash I use for facecoats, getting darker in the steamy heat.

The mold had negative slopes in places, which means that the glass powders would slide and fall out of place during firing. So I took the mold through a drying cycle to get out most of the water. I wearily dumped talc into the now-dry fritpack, up to the brim, to hold things in place.

(Note: If you put talc into a wet, just-packed pate de verre mold, without first drying out the water, the talc will cement itself onto the glass and you’ll need a jackhammer to get it off. Ask me how I know this.)

I sleepily calculated a firing schedule for the additional insulation provided by the talc. Somewhere along the line I completely forgot about the excellent insulation provided by firebrick. I had, in essence, built a baffle against the heat around the main area of my sculpture. It might not have mattered if I’d adjusted the schedule for hotter, longer firing.

That was mistake #7. The really, really fatal mistake. But I didn’t think about it then; I was tired. I took a shower and went to bed.

Firing over, I opened the kiln. Triangle’s edges were perfectly fused; the colors were exactly right. Thrilled, I started scooping out talc to see the rest of the piece…and a bunch of dry frit came with it. The combination of an effective heat baffle and insulating talc had done their job: Very little heat got to the faces in the mold, and the center frit never fused. What I essentially had was a glass ring with holes where faces should be.

Single-use mold, now crumbling. No silicone master mold–the piece was destroyed, with no undo button.

And just for added spice: I’d forgotten to remove my brand new kilnshelf before making the sandbed. NEVER cover most of a kilnshelf with an insulator, especially a wet insulator, and leave the rest of the shelf out in the open. Thermal shocked, it shattered.

I dumped the whole thing in the trash. Must admit I got a bit teary over it, but it was my own silly fault for rushing through technical stuff when I should have simply gone to bed.

I tried to get on with the next sculpture, but that piece (and my stupidity) bugged the life out of me. No matter how much I tried to start something else, they hung there in my brain, like a reproachful mother-in-law. Dammit.

Finally, I set out to do it again. That’s Part III.



  1. cynthia December 20, 2009 at 11:53 am - Reply

    No problem, Brian…Hmmm. Olympic USED to sell R&R, that’s where I bought it. I’ll have to update. Yeah, Seattle Pottery is great–I just got 500 pounds of my investment mix from them–no matter how much you order, and they charge $80 to deliver it to Portland, which makes it a good deal. And they custom-mix my soon-to-be-favorite face coat for me as well…

  2. Brian Berman December 20, 2009 at 8:48 am - Reply

    There is something about this learning curve that keeps me feeling like a newbee in school. My inner kid loves to sculpt – to play in the studio with clay, wax and even stone. My environmentalist self is upset every time I make a mistake and waste materials and energy. The costs of education are always factored in or out of the equation.

    On another note, I appreciate your resource list. I followed up with a request to Seattle Pottery about premixing ingredients and they offer a very good price based upon the mix you want. I asked about 500# of 50/50 Pottery Plaster and Silica Flour and they quoted $190 in 25# bags. I paid $180 for the dry ingredients in 50# bags. They said they need one week max to do it.

    On the other hand, Olympic Color Rods doesn’t sell R&R like your list states, so I’d remove them as a source for that.

    Thanks for all the information you are providing and wish you well with your castings, and your blogging. This probably should be posted to your Julie/Julia blog, as the appreciation theme is running parallel in these comments to your blog. I will continue to write you on that blog…..

  3. cynthia December 20, 2009 at 12:55 am - Reply

    Wow, Brian, thanks. That’s really a wonderful thing to say. I have to admit, I was more than willing to let this one go–it literally wouldn’t let ME go. I redid it as much to get it out of my head as anything else. I’m fairly happy with the finished result, which I think posts tomorrow (I write this stuff in a great rush, then spread the posts out over time.)

    Casting’s tough–I firmly believe that pate de verre is tougher. More steps, more opportunities to screw up. I’m a beginning caster myself, and I find that documenting mistakes in this blog forces me to think them through, figure out how to prevent them, and move on. I notice I tend to talk about 5X as much about the mistakes as the successes; I think that’s because all a success does is confirm what I already know. A mistake is a whole school itself. (Of course STUPID mistakes, which these mostly were, don’t count.) 😉

  4. Brian Berman December 19, 2009 at 9:42 pm - Reply

    Please know that I appreciate your sharing this tale. I think it better titled, the Sculptor that Didn’t Die. I am curious what keeps you going, with so many mistakes in one sculpture. What gets you up again after such a loss. No gallery or art buyer knows this pain. When they see the finished glass sculpture, they wonder why it costs so much. They don’t know that it might have taken a dozen attempts to get it right. This process is so full of quicksand and snares just waiting for one small step off a formulaic path.

    I appreciate you sharing these mistakes, as they teach a beginning kiln caster like me, that there are dangers at every twist and turn in the casting process. The joy of sculpting and the pain of mold making don’t fit well inside creative types. I know that mistakes teach me, and sometimes beat me. I look forward to seeing the resurrection of Triangle. Your sharing this process gives me strength to go onward. Thanks, Brian

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