I have been metalworking here and there since my last post, nothing really productive, just tinkering. It has been unseasonably cold here in Georgia, just had some snowfall this week, and the winter gloom has been making me yearn for summer again. This past summer, I managed to find some time to try casting bronze. It was a learning experience, a trial and error affair to put my theoretical knowledge into practice, and it is another example of making something new and bright with little equipment.
My goal was to cast a copper-alloy bolster for an ongoing collaboration I'm doing with Luke Shearer (http://lukeshearerbladesmith.wordpress.com). I was lucky enough to meet Luke in person at this year's Oakland Axe'N Sax-In, which I thoroughly enjoyed and will discuss in another post.
Like most of what I do, I wanted this process to be natural and enjoyable and done close to the earth - literally in this case. I tried casting the bolster twice, both times using open-top molds. The mold used in the first attempt was made from a haphazard mix of clay, sand, and grog and was contained in an old saucepan for ease of carrying. The one used in the second attempt was made of soapstone, which I enjoyed preparing and much prefer for this kind of activity. I wasn't happy with the results of either attempt to cast the bolster. I ended up forge-soldering it from two pieces of sheet bronze, and again, I will save this for another post.
As an impromptu part of the casting experiment, I made a small Mjölnir pendant as a test casting before attempting to pour the bolster. I impressed the hammer shape into some leftover clay using a broken twig, and quickly dried the resulting mold using embers from the fire. Moisture and casting do not mix, and I probably wasn't working with "safe" levels of moisture in my molds. I'm sure if they weren't open-top molds, gasses could have been a problem and popping, bubbling metal could have jumped out at me. Luckily that didn't happen, and while I wasn't happy with either attempt at the bolster, I did end up with the pendant and I had a lot of fun.
Here are some photos of the process. Looking at them again makes me feel much warmer.
Here, I'm preheating the crucible outside the hottest part of the fire. I also warmed my tongs in this way and rotated the crucible periodically until I was sufficiently satisfied it was preheated and moisture-free.
I was melting a variety of metals - silicon bronze, pure copper, and the zinc-laden yellow stuff, brass. I wore a ventilator with fume-proof filters since I am paranoid about zinc intoxication, and rightfully so I think, as it's very dangerous. I drank plenty of milk before and after this process, which sounds like an old wives tale, but it allegedly helps the body filter out the zinc and other metals.
Putting on my Fire Boots, or moving the crucible around, my memory is fuzzy.
Here, the metal is starting to melt and get a slick appearance.
My patented saucepan mold-holder.
Here's the failed pour into the failed clay mold. You can tell from the photo even that the metal was too cool to pour. It's more the consistency of honey at this point, and it should be much less viscous. Live and learn.
Here's the result of the failed pour. Not much of a bolster, but bright hot metal is always pretty to look at.
And here's the only survivor, the pendant, after a little cleanup. Despite its simplicity and unfinished character, I think its a pretty neat, charming little object, and I had fun making it.