Bronze Casting Session No.5

Last time we melted and cast bronze, we figured we had to build a new furnace since, after ten firings, ours had a serious crack in it. But then we thought, instead of doing all that work, maybe we could get away with wrapping ceramic fibre around the furnace. Here's how it went.

We loaded up our crucible and set it into the furnace after the charcoal was burning well. And then we piled on the charcoal to completely cover the crucible, and waited.  

When we first melted bronze and brass, we didn't need any external air source; the natural draught provided by the three entrances along the bottom of the furnace were sufficient. But since then we haven't been able to melt bronze without adding forced air from bellows. Perhaps we haven't been loading the furnace with charcoal correctly, and the entrances at the bottom are getting blocked by small bits of charcoal. Perhaps it's time to re-read the original paper that guided our building of this furnace.

However it is, after 2.5 hours and quite a bit of fresh charcoal added on two occasions, we realized the bronze wasn't going to melt without the bellows. Once they were going, it took not long at all, and we were ready to pour.

We realized that most of our interest in this session was in seeing how the furnace would work, how quickly or efficiently we'd get up to melt temperature. Because when the bronze was finally molten, we poured it into the molds without too much thought or expectation about what would turn out, as if the casting were a bit of an afterthought. So we were quite surprised with this glimpse when we cracked the first one open:

In the end, two Venuses came out very well, but the symbol of the School didn't. 

So we know we can get to temperature no problem with the bellows, but why can't we without them as we had initially done? In a way, it doesn't matter - the point of this could be simply to cast bronze and learn about that material. But that failure to repeat an outcome with consistency (a familiar experience in the Craft) indicates a lack of understanding of the process as a whole, and it's worth diving in there to see what we can learn. Beyond learning about this furnace, exploring the issue might reveal something more fundamental about our brains and way of working, e.g. is there a tendency towards taking shortcuts? Is there a lack of attention paid because we assume too quickly that we understand how it works? Or is the furnace perhaps just breaking down and in fact this is all we need to learn?