Foundry - Polygons in Bronze: Part 8

The ceramic component of "ceramic shell", is much like traditional ceramics in that it must be fired in a kiln so that it may vitrify. As it does so, the shell turns from a greenish-yellow to black (caused by soot) to a bright white.

With my vitrified shell, I am almost ready to cast some metal. However, to make sure that my mold doesn't break apart (at the enormous crack) under the weight and pressure of the metal, I needed to first patch the crack with furnace patch or refractory cement. This applies much like body filler or spackle. After applying the cement, I hit it with a torch to quickly harden it.

The casting process was a group effort. At the lead was our professor, Jesse Blumenthal, instructing us and making sure the operation ran smoothly. Two people needed to work in sync as they used a large, heavy metal pole that served as our crucible tongs. The crucible is huge, heavy, and made of graphite. It sits inside the furnace and contains the metal being melted inside. As the furnace is being heated up and metal is melting, the shells must also be slowly heated inside the kiln so that they aren't shocked by the heat of the molten metal. To facilitate the transfer from the kiln to a bucket of sand are two/three other individuals: one carrying shells from the kiln atop a piece of kao wool (a thermal insulating wool that is used to make kilns, forges, furnaces, and the like), and one or two others that are partially burying the shells in buckets of sand (the sand is there to keep the shells upright, catch any spills, and even act as a light insulator to reduce the heat loss of the shells).

For each crucible full of metal, we were able to fill multiple shells at a time, often without much need to fill the ingot molds. Everyone that wanted to take part in the casting process was able to in some capacity while the rest of the class was able to watch this spectacle which even lured onlookers from nearby classes.

My shell was the last to be poured during our first week of casting due to the sheer volume of the sculpture requiring more metal than was able to be allocated when pouring 3-4 shells at a time, as we had been doing. I was lucky enough to be able to pour my own bronze, something I am very proud of. Of course it is all a group effort, but to be able to say that I was the one that poured the bronze makes me very happy. Well, one of two, because I couldn't carry the crucible alone... The crucible full of bronze was very heavy and the heat that emanated from the furnace was sweltering. After we poured our shells, we had to fill some ingot molds... which required us to get real low and rotate the crucible very awkwardly. My grip strength gave out entirely, requiring me to rest the large metal pole on my wrists to keep it from falling. By the end of the process my arms felt numb. It was excruciating yet exhilarating.

After letting the shell cool overnight, I cracked it open. Using a chipping hammer, I broke the large portions of shell off of the bronze. I then used a small pick to dig out the more stubborn and small pieces of shell. Once the majority of the shell was removed, I cut off the pour cup and sprue with a hacksaw.

The crack did create some flashing, the most noticeable of which is on the back of the cat, but overall the cast came out great and captured all of the small details quite well.