Casting a wax proof from the mold that is free of defects begins the process of making a bronze casting. Ideally, the wax cast is not solid, it is wasteful, and I have had problems with the wax expanding the eventual ceramic shell mold in the burn-out kiln, cracking it. (ceramic shell investment casting) What I want is like this, another piece I’ve been working recently.
This is Victory brown sculptor’s wax. Usually dark brown, but in other off-colors lately from my supplier, which is annoying. It comes in ten pound slabs,
which I melt down in this kettle, enough to fill the mold fully.
The idea is to fill the mold, allow it to cool briefly, and pour out the excess, leaving a hollow form with walls about 1/4 inch thick. The trick is to get the wax to the right temperature; too hot, and the walls won’t cool enough, be too thin, and the hot wax pouring out will re-melt carry away the wax around the pour hole; too cool, and the wax won’t take on the surface details of the mold correctly, or flow evenly throughout the mold. By experience, the correct temp is between 155 degrees and 160 degrees. Of course it takes more heat than that to melt the wax, so use a kitchen cooking thermometer to measure as it cool to the right temp. Essentially it is the temp where the wax begins to solidify from a liquid; it gets soupy, and begins to build up on the sides of the pot, instead of staying thin and watery.
Mount the mold in something securely. A lot of hot wax is dangerous.
Pour it in a steady stream. For this mold, I let it cool then for three minutes.
Invert the mold, and pour out the remaining liquid wax.
This is the little mold for the two head parts to the sculpture. These get re-attached to the main piece later.
Allow time to cool completely. Opening the mold too soon, while it is still warm, can deform or tear the wax apart if it hasn’t completely re-solidified. Here’s the fine result I was expecting
Wow, I’m pleased. That’s a very complicated form to get from a two piece mold. I put a lot of planning and work into this, and the proof is in the quality of the cast. This wax needs very little clean-up to be ready for the bronze casting process. Mostly just cutting the spouts from the head and feet, and smoothing the reattachment points lines on the head parts.
I won’t actually use this one, it was a test. I’ll pour several more, and pick the one or two that I like best to cast bronzes of.
Oh, there is still a lot of work to do. I’ve had some time off, but now I need to push on, and get this done.
There are other sculptures filling up my head that I want to get started.