As I recall, the metal (I've seen both silver and 22k) was poured into a dishtowel once (not the terrycloth kind), and a piece of muslin the other time. The cloth was wetted and then suspended- I forget how- as a sort of hammock in the bucket, with its lowest point a few inches below the surface.

The theory was that this would make a nice, large, clean lump or the metal. I haven't seen it work that way yet; it's ended up in some pretty cool organic forms, though. of course, no one involved has made a habit of doing this; it's always someone wanting to try it because they saw someone who does do it regularly succeed, or heard about it, so I'm sure some of the finer points were missed! Still, the results were cool, even if not what was intended.