On pour days the ceramic shells must be pre-heated to prevent them from breaking when the molten metal is poured into them. The shells are once again loaded into a cage (this time right side up) and raised into the kiln. The kiln is heated to ~1350 degrees farenheit. While the shells are pre-heating the bronze furnace is being charged and solid bronze ingots are melted in preparation for pouring into the heated shells. We melt 750 pounds of bronze in one charge. The flame of a charge appears green due to the metals in the alloy of the bronze but mostly due to the copper content. We heat the bronze, the shells and the ladle with natural gas.Once the bronze is completely melted it is allowed to heat to pouring temperature. A member of the pour team will check the temperature with a pyrometer to make sure it is the proper temperature to pour into the shells. Our shells may be poured at a variety of temperatures, ranging from 1950 degrees farenheit to 2100 degrees farenheit.
The temperature a shell is poured at depends on its size, thickness and complexity. Our pour captain must carefully plan each cage to ensure that we will be able to pour each shell at its appropriate temperature and have enough metal to fill every shell at the correct temperature, Once the temperature is checked and the metal is ready, the cage of shells is removed from the kiln. The molten bronze is poured into a ladle so that it can be poured into the shells in the center of the pour room. Our team wears protective kevlar pour suits. Inside their suits temperatures can reach more than 140 degrees farenheit! The team will often wear ice vests in an effort to maintain core cooling - even in the coldest winter months this is a very hot job.
Anyone who works in the foundry has an opportunity to be a member of the pour team. We rotate members on a regular basis and every member on the team takes each of the roles on the team, every Saturday. Those positions are Pour, Shank and Buttons.
Our Bronze is an alloy of 95% copper, .02% lead, .02% tin, 06% zinc, and 4% silicon.
