When I received an opportunity to cast bronze in Austin, Texas, at the Atelier 3-d with artist and teacher Steve Dubov, I signed right up. Always interested in process, Steve uses a different kind of investment mold and alters his technique for the lost wax bronze casting method.
So, I created a couple of new sculptures in wax. In my art post on April 15, I shared something of my creating the sprue, the wax sculpture connected to a wax funnel that will all ultimately become bronze.
While I need my wax welds to be strong, these things are a bit fragile and oddly shaped, each sprue being individual. My bumpity dirt driveway that is almost a mile long helps nothing. So, I have transported the wax floating in a bucket of water.
This greatly diminished the vibration and shock on the piece, although I still had water sloshing around in my car. Sheesh, I must continue to fill the driveway potholes with stone chips!
In the image above on the left, air conditioning metal tubing has been used to create a "mother mold" (the outer supporting mold). The next image shows me holding the sprue. Below, I am holding my sprue to keep it from floating, pour funnel at the top opening with the sculptures deeper, parallel to the side walls.
Steve is pouring a mixture of plaster, playground sand, and water into the mother mold. Once this mold has set, holes will be lightly punched into just the metal tubing to release steam later during the pouring of the molten bronze.
After the mold is ready, it will be heated and all of the wax will be melted out (hence the term "The Lost Wax Process" in bronze casting).
Now the sculpture is only an air space. Bronze will be heated to about 2000 degrees F so that it becomes a liquid. Then it will be poured into the funnel-shaped opening, travel down the air space, follow the sprue space to fill the sculpture space, and then chase air out the vents. The bronze begins cooling as soon as it is poured, so everything in the pour moves fairly quickly.
I did not attend the bronze pour since I was working in my studio on my stone carving. This fourth image shows you the bronze pieces after Steve cut away the mold and then cut apart each sculpture from the cooled bronze sprue parts. He left some of the sprue on so that I could put the art into a vice as I chase the metal.