The mortar we cast is a reproduction of an eighteenth-century one in the Colonial Williamsburg collection. Military forces used coehorn mortars extensively during the eighteenth century, but our original was privately owned and probably was used for fireworks or signaling. We chose it as a test piece because it is relatively small and therefore a good place to start with learning the model- and mold-technology and testing the furnace.

We now are in the process of turning the outside of the casting. As we do so, we are realizing that there is some porosity (small bubbles) at the surface of the casting caused by gas in the bronze. If machining the surface removes most of these, then we probably will bore the mortar and, eventually, test fire it.

If the resulting surface is not satisfactory, then we probably will not take the time to bore this particular piece. In either case, it is serving its primary purpose: indicating to us what we need to do to produce clean castings.

We now know that we need to determine how to eliminate gas in the molten metal—and we are continuing to study the original documents to see how better to do that. We’ll post a photo of the mortar casting after it is turned, so that everyone can see the results.