Casting Organics

CASTING ORGANICS

By Mary Sugrue

Our casting & production manager, Mary, gives insight into the world of melting and shaping precious metals.

Casting is an unpredictable art and science, and every time, fingers are crossed, willing the metal and mold to behave.

There are a myriad of things that can go wrong with any casting, and it’s usually through trial and error that these problems are solved. Molds can break down; metal may not fill or overheat and become porous. Each of these problems are a balancing act and require precision in a process that is half luck and half expertise. This is all true for Lost Wax casting, a process that is thousands of years old. Wax is a material that is well understood and optimized for casting, but even it can have issues if all parameters are not met.

Casting is even trickier when using sub-optimal materials like Organics and Found Objects. The main concerns when casting organic materials is making sure they burn away cleanly, leaving no ash or residue in the mold, and that the materials they are made of don’t react with the investment plaster to erode the detail and stability of it.

The Burnout Schedule takes care of the first portion, which is the rate and temperature at which the mold in the kiln is fired. By holding the flask at specific temperatures and certain times, you can make sure that all burnable materials are removed. However, because you might be putting anything and everything in there, all with different ignition temperatures, there is no specific Burnout Schedule for organic materials. Bone, for instance, may take extremely high temperatures for an extended period to entirely turn to ash, but small twigs can be removed much more easily.

The second concern is handled by preparation. To keep the investment from interacting with the materials, using a variety of substances to seal them away from the mold is critical. In these casts, I used a mixture of beeswax, shellac, and a low melting temperature, pliable jeweler's wax, often referred to as pink wax. I evaluated the surfaces of each item to gauge what process would be most effective at both sealing the object and retaining its texture before applying it. In this manner, I was able to preserve even some microscopic details, though many will be lost in the overall polishing.

“The thrill of seeing the result of a casting is so exciting because it’s never certain. It takes several days of preparation and the moments to know if your effort was successful; truly a job that keeps you on your toes.”