Using wax clay

A review of J.F. McCaughin's Sculpting Wax

This post was originally published on my old blog in 2008. I thought it deserved a replay. It’s also inspired me to go find the sample piece I’m showing here, one of my hosta bowl series, and see if I can’t finally finish the thing.

waxworx-wax clay

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 earthen clay. Wax is less immediate, giving me far less control and even less visualization of the final product than earthen clay. I enjoy the Zen-like absorption I get into when tooling wax…but I miss the joyful, near effortless control possible with my favorite water-based clays.

So when Hugh McKay, probably the most gifted glass caster I know, suggested that wax clays that might give me the best of both worlds, I leapt at the chance and bought some.

The product’s from J.F. McCaughin, in Rosemead, Calif., their “Sculpting Wax” AB300-series. I ordered “Firm/Tan” (AB330) from Arizona Sculpture, a handy little sculpting supply house with an infernally slow website but nice prices and fast, friendly service. Right now they’re selling it for about $4.75/pound, about a third again as much as a good victory brown.

For what it’s worth, I pay less than a tenth of that, about 45 cents/pound, for my favorite Hanjiki porcelain clay. Of course, wax clay is ready to go straight into a refractory mold, too. With earthen clay, I usually create a silicone mastermold and hard shell (mothermold), then make a wax, so it doesn’t save much time and probably doesn’t do much for my finances, either.

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

Anyway, my sculpting wax arrived in a paper-wrapped slab, like most waxes. With its color, it looked uncannily like Caucasian 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 cheaper plastic clays such as Sculpey. It cuts easily, softens to workability in the hand. It’s best worked with a [tooltip title=”a banker’s file box, lined with aluminum foil, with a hole cut in the top for a cheap clamp light. It gently warms the clay to workability.”]clay oven[/tooltip].

If you push your finger over the warmed wax to smooth it, you’ll feel a bit of grain, about like superfine sugar. However, if you’re careful you can smooth and polish it while warm.

I had just the project for it: HostaBowl, a bowl of hosta leaves joined together like a flower, with a central group of figures instead of stamens. The figures had been giving me trouble–I really wanted to sculpt each figure individually in clay so they would be different. Unfortunately, I could never have removed the clay from the mold, and I just didn’t see the point in making a silicone master mold and then retooling each figure.

Even better, the majority of the piece is done in victory brown wax, so I had an excellent basis for comparison.

The figures are about 3 inches in maximum length, with lots of detail. That was small enough that I could keep enough clay for the next figure warming up in the water tray of my soldering station. The tray picks up just enough residual heat from the station to keep the wax soft but not runny.

(Techbuddies who see that I’m melting wax with my fancy electronics soldering iron react about like Mom does when I cut wire with her dressmaking shears. But that station is great for wax.)

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.

It seems to have a “memory.” Even if I do a classic plastilina-style join, i.e., scuff up both sides, heat them enough to get them a bit runny and meld them, the wax clay join WILL come apart under moderate stress. A victory brown joint wouldn’t. (nor would earthen clay)

Wax clay is also heavier than victory brown, and must be supported if you don’t want appendages to fall off. 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.

The wax clay 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 cold 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 temperature-sensitive 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–the warmth of my hand quickly deformed the wax clay.

The wax clay was also slower to cool. I’d recommend keeping an icepack or freezer handy–it really speeds up your sculpting with this stuff.

The softness also meant that the wax clay took less detail and needed freezing for best performance, at least at the small scale I was working in. I suspect that this stuff is actually better suited to larger work, if only because the crystalline grains of the clay can get in the way of the smallest details.

The softness and temperature sensitivity were liabilities, as far as using wax clay to construct master molds. It’s fragile, so any alginate or RTV silicone process tended to deform these small pieces, making them difficult to remove. If I keep working with this stuff, I think I’ll need to freeze the clay overnight, THEN make a silicone box mold for such things.

Once you’ve invested your wax with whatever mold mix you’re using, you steam/burn out the wax to be left with a (hopefully) perfect investment shell for filling with glass.

I had a much larger mold with a victory brown model that needed steaming out,  so I set up two steaming units, one for the big mold, and one for my wax clay figures, and started them together.

Both steamed out acceptably, but completed in almost exactly the same time. The victory brown washed out of the mold in streams and left little residue. The sculpting clay took forever to steam out, and tended to come out in gobs. In the end, I wound up washing out the mold several times with boiling water. Even then, it tended to leave a sticky crystalline goop on the mold walls.

So…while I was pleased with the sculpting quality of this clay and prefer it to victory brown for hand-forming, it’s not really the best of either world. The brown leaves a nicer mold; the earthen clay is much better for sculpting.

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

2014-09-08T21:45:33+00:00

4 Comments

  1. Shereen Timmerman October 20, 2014 at 11:51 pm - Reply

    Your posts and wealth of information AND being so generous to help others is wonderful.

  2. Diane Weiland July 3, 2014 at 10:37 am - Reply

    Great imagination, I love.

  3. Frances Zolnikov June 5, 2014 at 11:25 am - Reply

    Enjoying your travels with glass. Neat work!

  4. haunt rama June 5, 2014 at 8:35 am - Reply

    Fascinatingly interesting and valuable. Beautifully designed.

Comments welcome! (thanks)

%d bloggers like this: