Convergent Series

learning, using & teaching metal clay, and other aspects of life

White bronze clay! First-time Trials and Tribulations…

Posted by C Scheftic on 2010/08/30

Time to try yet another base metal clay: white bronze from Hadar Jacobson.

When trying something new, it’s fun to have another experimenter nearby to compare notes with. So, once again, I headed up for a few days at Alice Walkowski’s great “Ally’s Art” studio at the National Transit Building in Oil City, PA. (As last month, Alice’s student Virginia was there one afternoon too, now working on a gift for her daughter: I cannot risk giving away the “surprise” but the recipient should be delighted by the artistry and impressed with all the effort in that!)

One afternoon Alice and I each mixed up a batch of white bronze powder and explored working with the resulting clay. Alice posted her version of this story. The mixing process and working properties of white bronze are very similar to those of the yellow bronze I described last month.

Hadar suggests, particularly with white bronze, starting with plain “test pieces” that are the same size (in all dimensions) as the “real” ones you intend to make. How to make “test” pieces with all the quirks of real ones?! I just made simple “real” pieces for my initial tests. Shown first is a partially-polished holiday ornament. It’s the first piece I started to “clean up” after firing, and my immediate reaction was positive.

That feeling did not last as long as I’d’ve liked. Shown next is another attempt at a holiday ornament. It started out the same size as the first, though with an outer border that had been rolled a bit thinner. (That difference was not intentional but, when I noticed it in the drying clay, I chose to leave it, hoping the “sturdiness” of bronze would make that OK.) As I began to clean up this piece after firing, bits of corners and edges broke off. They looked solid: no sign of darker, unsintered clay. So I took a pair of pliers and easily broke off the border down to the thicker center square, then filed those edges smooth. I can try to “reclaim” this with a future experiment in adding a backing layer or other hanging device….

Since my first trials with copper and yellow-bronze involved making little fan-shaped charms, I wanted to try a couple of those in white-bronze too. (These are actually the first pieces I made with white bronze powder: I’d mixed a small batch and formed two fans during a demo of working with clay powders at the August meeting of our local metal clay guild.) Somewhat reminiscent of the edges on the second ornament, above, the fans had thin little tassels that quickly broke off. In other ways, however, these pieces appeared to have sintered.

Now, I’d had tassels break off of a few of my earlier copper and yellow-bronze charms, but only when they’d shown other signs of inadequate sintering. But something else happened with my second white bronze fan charm. As I began its post-fire clean-up, it slipped off my polishing block, landed a mere couple inches down on a metal table-top, and broke. I’d seen no previous sign of cracking, and the relatively thick edge along the break had the white-metal color that I took to mean it had sintered (i.e., I wasn’t seeing the original darker clay). Though I did no more polishing on the front of the piece, I did try polishing up a bit the edge along the break, and it continued to show a solid metallic-shine.

Alice made some pieces too; we fired all of ours together in her SC-2 kiln (muffle-style, front-loading). We generally made “pairs” of pieces, arranged them symmetrically in our firing box, and mapped out where all of them were placed.

These two had been placed along the sides. They were closest to the front, but there was still a good bit of space between them and the door. They had seemed OK at first, as I tested and polished the backs. But once I got a bit more aggressive in polishing the fronts, the dreaded “dark clay below” began to appear, a clear sign that they hadn’t sintered fully. (It’s very obvious on the right side of the piece on the left; it’s also visible elsewhere on that piece and on the one to the right.) These will go back into the “to be fired” box for now; although I have some doubts about how the buffed-down-to-clay parts will look after firing. But these are test pieces, to see what happens.

Despite problems with sintering and breaking, however, the thing I find most frustrating about these “base metal clays” is how few you can fire in a single load. I don’t mind (much) the fiddling with carbon and firing boxes. I don’t mind (at all) the limits on torch-firing (I prefer using a kiln even with silver pieces, not because using a flame bothers me, but because I prefer “full firing” at highest temperature and longer times). I don’t mind the multi-step firing programs, nor re-programming the kiln for different metals or combinations of metals. I don’t mind the longer firing times (e.g., close to 5 hours for this “quick fire” white bronze), plus longer cooling times. But, in comparison to the simple firing process with precious metal clays, if it’s going to involve that many extra steps, and that much more time, then I do wish that I could load up the kiln with as many pieces as I can when firing silver, instead of just a fraction of that amount. Hadar seems to be working on some alternatives that could prove helpful so, at least for now, I’ll remain optimistic.

I will try doing a bit more with these base-metal clays when I find spare time. (And write up some notes for here.) From a design perspective, I really like the possibilities from combining several different colors in a single piece. (But I’m not going there until I’ve mastered the firing quirks of the separate metals!) From a teaching perspective, I’d been hoping I could offer base-metal classes where I could charge less for the materials while also letting folks make larger pieces. But if it’s going to take multiple hours-long firings just to complete the pieces for a class, then any savings on materials will be eaten up with larger registration fees to cover everything involved in those firings. I’m not saying I won’t, eventually, both produce pieces and teach classes using these clays. I’m just saying that I’m waiting until more of the kinks in firing them have been worked out before I get as enthusiastic about them as I am about precious-metal clays.

Back to silver for a while!

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