||[Dec. 5th, 2006|01:21 am]
Insomnia strikes, so I write.
A few days ago, I spent some time casting. Tried a longer, skinnier sickle blade and an idea I had for a fantasy piece of a sword.
The longer, skinnier sickle didn't quite make it all the way through the greensand mold, but enough got through that I can just braze a bit on for the handle and it should be good. The sword blade, though, I'd learned on a previous attempt wouldn't make it through such a long, thin hole in cold packed sand, so I tried an open face mold, also of greensand.
I'd call it quite a success. Not only did it come out, but even though it's a bit thick at the base, nearly 1/2" (pretty impressive since the pattern was made of 1/4" MDF), the tip is about 1/4", almost ideal -- and I can easily grind down the overly thick bit. As a plus, the upper side of the casting has a very neat reticulated surface -- think lots of neat, multi-colored ripples.
(Reticulation is caused by the differential contraction rates of the different metals as they cool -- so bronze, a mixture of tin and copper, reticulates pretty well. Or I could be wrong, and this is just an artifact of casting in an open-face mold, but it's pretty nonetheless. Since different parts of the sword are of different thicknesses, and therefore cooled at different rates, there's also some variation in surface coloring -- from blue to purple to shiny to green.)
I don't know that I'll be able to preserve the reticulated surface, but I think I'm going to try -- worst case scenario, I grind it off later.