Using wax clay

Work in progress with wax clay, on victory brown

As you might have guessed, I’m not a great fan of the waxes used in lost wax casting, mostly for the mess they make. However, after trying diligently for a couple of years to find an alternative I reluctantly came to the conclusion that wax is still the best option for my casting style. Drat.

Much of the pleasure I get from casting comes from playing with the clay. For me, wax is less immediate, and I have less control and less visualization of the final product in wax than in clay. I enjoy the Zen-like absorption I get into when tooling wax…but I miss the joyful, near effortless control possible with clay.

So when Hugh (glassburl on warmglass.com) suggested I try a wax clay that might give me the best of both worlds, I leapt at it.

The product’s from J.F. McCaughin, in Rosemead, Calif., their “Sculpting Wax” AB300-series. I bought the “Firm/Tan” variety (AB330) from Arizona Sculpture, a handy little sculpting supply house with an infernally slow website but nice prices and fast, friendly service. A 10-pound slab was $35, $3.50/pound, or a bit more than I’d pay for “victory brown” microcrystalline wax.

For point of comparison, I pay 45 cents/pound for Hanjiki Porcelain, my favorite clay for model-making. Of course, I then spend a few days coating the model with silicone, urethane or latex and and a shell material (plaster, resin, etc.) to create a mother mold so that I can pour molten wax into it and make the actual wax that goes into the final investment, so I’m not really saving that much. And the wax almost always needs to be tooled and refined before actually being invested, so it doesn’t really save that much time, either.

–sigh– There just ain’t that many shortcuts in glass sculpture.

Anyway, the sculpting wax came in a paper-wrapped slab, like most waxes, looking uncannily like flesh. (In fact, I wonder if this isn’t the “forensic wax” that’s used to reconstruct the in-life appearance of a dug-up skull.)

In appearance, texture, and workability it’s very much like a coarse plastilina or something of the Sculpey/Fimo ilk. It cuts easily, softens to workability in the hand (or in a “clay oven,” constructed by cutting a lamp-sized hole in the lid of a file box. lining the entire box with heavy aluminum foil, attaching the lamp to the lid and putting the clay inside). It’s got a little grain in the clay matrix, one that feels a bit like superfine sugar when you squeeze it hard through your fingers, but it smooths and polishes nicely.

I tried it on my current headache, er, project, HostaBowl, to make the central figures (shown at the top of this page). They’re about 3 inches in maximum length, with lots of detail, so it was a good test for the stuff. The nice thing about working so small is that I could keep enough wax clay for an entire figure in the water tray of my soldering station, softening. The tray picks up just enough residual heat to keep the wax soft but not runny.

(BTW, my bytehead buddies who’ve discovered that I’m melting wax with my fancy electronics soldering iron react about the same way my mother did when I cut wire with her good dressmaking shears. But that station is a wonder on wax.)

You control earthen (waterbased) clays with water; you control plastilina, sculpey, and this wax clay with temperature. Chill wax clay in the freezer and you can polish it, although not quite to the degree of victory brown. It takes impressions easily, again not quite as easily as victory brown, but it’s a lot more sculptable. The light color lets me see more detail than victory brown, which is a big plus.

The wax clay sticks to itself well, but may have a “memory.” Even if I do a classic plastilina join, i.e., scuff up both sides, heat them enough to get them a bit runny and meld them, the join WILL come apart under moderate stress. The wax clay is also heavy, without much structural integrity. The figure on the right in the picture above is bowing her head; the head and hair had to be supported to prevent neck fractures. When I was setting these figures up for investment neck cracks were a continuing problem.I’d probably have the same trouble with plastilina or any grogless water-based clay.

Since the main part of this sculpture was done in victory brown, I had an excellent opportunity for comparison. In general, the brown wax had a more flexible working temperature range and took fine detail better.

The wax clay couldn’t take quite as much heat and retained it longer so it was slower to solidify. It could be smoothed and polished with the fingers more easily than the brown. It also was more likely to “crumb up” when I dragged a tool through it–I quickly learned that the tool needed to be moderately warm or the clay very cold, to make clean cuts. Victory brown’s a bit more forgiving in that regard.

The sculpting clay was also more sensitive to the temperature of my hand than victory brown, which meant I had to take a strictly hands-off approach to putting detail in the figure. You can grab a brown wax figure and tool it in hand; I found that–at least for these tiny figures–my hand quickly deformed the wax clay.

Remember that I’m working very small here, with lots of tiny detail. I suspect that wax clay is actually better suited to larger work, because the grain made tiny detail a bit of a pain to create.

Cleanup is a LOT easier with wax clay than victory brown, which could be sufficient reason for using it. As predicted, from the moment I melted my first chunk of brown wax it started appearing on walls, floors and clothing two floors above my studio. The wax clay seems to have less of a tendency to travel.

I’d originally thought that I’d treat the wax clay as I do my water-based clay–build a “mother mold” of the figures, so that I could invest the wax directly but also have a backup to make more if something went wrong. I can do that with victory brown but the wax clay proved very fragile. It was pretty mangled by the alginate or RTV process, deformed easily and proved difficult to remove. It doesn’t freeze as hard as victory brown, which may have something to do with it. I suspect I could paint on a latex skin, freeze the wax clay for a few hours and have better luck but at the moment I’m out of latex.

Once you’ve invested your wax with whatever mold mix you’re using, you melt or burn out the wax to be left with a (hopefully) perfect investment shell for filling with glass. I burn out outdoors, something I can’t do right now in freezing cold and rainy glassland, so I opted to steam. In this particular project I’m investing with hydroperm, a lovely mix for small projects. (Metalworkers say that hydroperm absolutely CANNOT be used for lost wax, but on the glass side of the house it’s sold specifically for that purpose. Odd.)

I’ve got a second project going that’s entirely victory brown, so I set up my steamout station to steam out a wax clay figure and the victory brown simultaneously. The brown wax in this case was at least 4x the volume of my little figures. Both brown and clay waxes steamed out acceptably, but it was a LOT easier with the victory brown. It quickly washed out of the mold in streams, with little residue.

Despite being much larger, both steamouts completed at about the same time–the wax clay is a LOT slower to steam out. Plus, it didn’t steam out as cleanly. It tended to leave a sticky crystalline goop on the mold walls. Doing something larger might take a very long time to steam, so I may opt for burnout the next time around.

Overall, though, I was very pleased with the sculpting quality of this clay and prefer it to victory brown for hand-forming. It’s still not my beloved water-based clay, but it’s an acceptable alternative.

Now to fill those molds with glass and get ‘em in the kiln…

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