Jonathan - Yes, I have tried "snow casting", and was very
disappointed! Unless you have snow which is granular from thawing
and re-freezing the molten metal just makes the snow disappear!
Fluffy snow doesn't have enough mass to cool the metal before the
metal has made a huge "pocket" (tunnel). I have used chunked up ice
cubes from bags of ice, in a metal bucket, and gotten fair results,
which is why I expect granular snow may work. The most interesting
alternate casting I've done is with a wet broom, pouring the molten
silver into a thoroughly wet broom-corn broom. Raises Cain with the
broom; be certain to have a pail of water to dump on it to stop the
smouldering; but, it makes an interesting pattern.