Investment/Ceramic Shell Burnout

With the wax finished and approved, the next step is turning it into a mold that can take molten bronze. This is the investment stage — building a ceramic shell around the wax — and it's one of the most exacting parts of the whole process. After 30 years doing this for contemporary artists and sculptors, we know the shell is only as good as the patience that goes into it.

First comes gating. We attach a system of wax channels, called sprues, to the piece. These become the pathways the molten bronze will travel through, so they have to be placed with the final pour in mind — guiding metal into every part of the form and letting air escape ahead of it. Poor gating shows up later as a casting that didn't fill, so this step gets real attention before any shell goes on.

Then we build the shell itself. The gated wax is dipped in a fine ceramic slurry and dusted with sand — fine grades first to capture detail, coarser grades after to build strength. For more than 20 years we've used investment materials from Remet Corporation, among the finest available, because the surface a casting inherits begins with the quality of the shell. Each coat must be completely dry before the next goes on — any moisture trapped between layers will cause problems down the line — and we repeat the process 10 to 12 times, until the wax is encased in a hard ceramic shell strong enough to hold molten metal.

Larger work is its own discipline, and our foundry is built for it. Our kiln and crucibles are sized to handle sections four to five feet high, which lets us keep big forms in larger pieces rather than chopping them into many small ones — less welding and chasing down the line, and a truer final sculpture. For these pieces we reinforce the shell with wire, mesh, and refractory cement and add extra coats so it can carry the weight and stress of the pour. We recently cast a large-scale monument this way, keeping the sections as large as our equipment allows so the finished piece needed far less welding to assemble. [To name the artist once permission is confirmed: "...a large-scale monument for [Artist Name] this way..."]

Once the shell is complete and fully cured, it goes into the kiln for burnout. The shell is brought up to heat carefully — rushing it risks thermal shock and cracking — and the heat hardens the ceramic to its final strength while melting out all the wax inside, which is where "lost wax" gets its name. What's left is a hollow ceramic mold, a perfect negative of your original, ready to be filled with bronze.

From our Oxnard foundry just outside Los Angeles, we shell and burn out every piece by hand for contemporary artists and sculptors across the LA area. With the mold cured and the wax gone, your sculpture is ready for the pour.