I’ve often cast small objects with scrap silver and occasionally
gold but, never tried to cast ingots to form sheet or wire. Is there
anything in particular or special that I need to know or do to the
scrap before, during, or after? I do have a rolling mill but, have
really only used it for applying texture to sheets. For casting
small objects, I would simply add a little casting grain or fine
silver in the crucible with the scrap. That seemed to finish &
polish-up just fine. The scrap that I have is a mix of cast and small
sheet pieces plus the inevitable faux pas. The casting I mentioned
was simply using delft clay (mighty handy little process) so I don’t
have a lot of previously cast. Although I have a pound or so of
silver, I only have less than a 1/2 ounce gold scrap. I would
appreciate any tips.
Regis, Producing such an ingot is not a problem, but no faux pas -
no dirt, no solder, no enamel, nothing in the crucible except clean
metal. Here is what you do for the silver: Soot the mouth and the
inside of the ingot mold generously with a torch (use no oxygen).
Position the ingot mold safely (a bit crooked) in a pan or other
recipient and heat the mold (gaz and oxygen) until it is so warm
that you cannot touch it any longer.
Soot the crucible (no oxygen, just blacken it), heat up the crucible
until the boric acid in it melts. Put the crucible on the mold, it
gives it some heat. Heat the whole crucible up, not just the bottom.
Use maximum heat but no oxidising flame. Melt the silver, put boric
acid (just sprinkle), remove impurities (I do this with a wooden ice
lolly stick) and pour in one movement. Don’t hestitate. It’s better
to melt too much silver than not enough. The surplus will end up in
your pan. Keep them together until you have enough and use them to
make an ingot.For that little gold, there is no need to use a
crucible. If you do anyway, you need a crucible for this type of gold
only. The better way is to use a hard charcoal block and carve a
sheet shape in it (I use a stainless steel ruler to do this), melt
the gold and when molten press it down with another charcoal block
(it doesn’t need to be a compressed one, but the surface has to be
clean and straight). Very easy, very quick, but make sure that the
indentation is big enough for the gold, otherwise it can spit out
when you press the second block on it. That’s all. When the ingots
are ready, don’t pickle. They should be clean. Hammer the sheet down
with heavy blows (reduce 10 - 15 percent). Anneal. Pickle and roll.