Hey, neat stuff YHR! I always wanted to get into metal casting and have looked at the low-temp alloys (fields metal, woods metal, cerrobend), but it always seems to require a lot of prep work and tricky mold prep. You make it look doable.

But, just an FYI for those thinking of trying this...a lot of the really low temp alloys include lead and/or cadmium, and as such are toxic. I would recommend taking precautions against breathing or ingesting particles or fumes, and watch that you don't track little particles(e.g. filings or sanding dust) into the house where kids might ingest them.
Looks like Micromark's 160 metal (160F melt point) contains both lead and cadmium and is most like Wood's Metal. http://en.wikipedia.org/wiki/Wood%27s_metal
The 280 doesn't, but melts at 280F instead. :P

D.