I’m in San Francisco for a class in casting at Revere Academy — MOLTEN METAL, AWWWWW YEAHHHHHHH — and wanted to share what I’ve done so far. There’s a lot to learn about the process, combining skills of working with wax, using molds, calculating metal requirements, setting up the investment (plaster mold formed around the wax or object), and the actual casting of the metal.
These are a couple of examples of succulents cast by my instructor, and the detail and texture on them is just mind-boggling. I was instantly obsessed with the idea, and hopefully tomorrow it will come to fruition! (More on that later. There’s a cactus of some sort, a sempervivum, and a zebra plant in that first picture.) I ran right out Friday evening and bought some succulents to
sacrifice for the greater good cast.
The first part of the class was to inject wax into molds (supplied by the school, unless you had your own), and assemble several waxes into a cast-able “tree” that fit the dimensions of the flask — not as easy as it sounds. This tree wasn’t actually cast — just an exercise in how to assemble a tree for casting. By angling things right, dozens of small pieces can be cast all at once, in one flask. (If you’re wondering, among other things on my tree is a LEGO stormtrooper helmet, and half a washer. You can mold darn near anything.)
I decided to cast one of the wax rings I made in Wax Carving class, back in August 2013, as my first actual project (green wax.) This first casting uses the centrifugal method, which is… action-packed. (I’ll get to that in a minute.) I mounted the wax to the base of the flask using sprue wax (yellow and red wax), which will provide a conduit through the plaster for the metal to be poured in. (What you’re looking at now will be upside-down, when cast. A sprue is just a conduit for metal to flow through, and one piece can have multiple sprues, to aid in the flow.) Once the flask is assembled, a kind of plaster called investment is mixed, put under vacuum to remove air bubbles, then quickly poured into the flasks, and then the flasks are put under vacuum to remove air bubbles from around the wax, which would mar the mold. There’s only about 12 minutes to go from mixer to poured, to bubble-free and sitting in a safe place, so the process is a little intense.
Maybe I should say, the class is a little intense.
So all of that was day 1. Once hardened, these flasks are placed in a kiln overnight to burn off the wax, and any carbon or moisture that remains, and held at a temperature optimal for the casting process (which varies; ours were 950° F.) Today was day 2, and we started casting immediately after lunch. Guess who got picked to be first? (I probably looked like a deer in headlights.) So here we go…
So. Centrifugal casting. (Did I mention I was being quizzed on each step in the process? NO PRESSURE…)
The open drum is wound up with a handle, that can be locked in place. You wind it up, then lock it, then place your metal in the crucible and start melting. Once the silver is perfectly melted and prepped, a partner places your flask (which has been in a kiln heating the whole time) next to the crucible, you take the torch away, and the partner unlocks the centrifuge, which spins at great speed, flinging the molten metal into your mold. (It’s a little scary.) Once the drum spins down, the flask can be removed, set aside to cool for a few minutes, before quenching it in water to simultaneously cool the metal and dissolve the investment plaster. Once it’s done violently bubbling underwater — INTENSE — you can pull it out and grab your finished piece! My ring turned out great, and it’s ready to trim, finish and polish.
In reality, it was a blessing to go first, because then it was done, I was relieved, and I could spend the rest of the afternoon preparing my second piece for tomorrow’s vacuum casting…
So in the end, I wasn’t able to use the succulents I’d hoped to cast as whole plants, due to space limitations. Instead, I created a “bouquet” of gollum jade leaves, and zebra plant leaves, which I mounted… creatively… into a flask. I won’t know until tomorrow how it all held up under the investment, but I’m hoping for the best! (Unlike waxes, organic items can’t be vacuumed once invested, as the vacuum will crush the organic materials and ruin the mold. You just have to tap the sides of the flask and hope all the bubbles dislodge before it hardens.) I will be casting it in bronze, as I love the look of the instructor’s examples, and it may be an opportunity to try some patinas, on my own time.
Tomorrow will be vacuum casting, which has less open swinging flames, but just as much molten metal (more, actually, since I’m making a larger piece.) I hope to have more action shots! A GIGANTIC thank you to Aussie classmate Diane for her barrage of photos of my casting experience!!
Thanks for reading to the end, and I hope you enjoyed the blow-by-blow commentary!