A suggestion or 2:
Pure copper is a very difficult metal to cast, dirty, oxides,
“sticky”, etc. If copper color is what is needed, one type of
coppery alloy to try would be “contact copper” (an alloy used to
cast electrical contact points). Or contact your metals supplier
and ask them what they have for casting that is VERY hig copper
Preheat the metal and the crucible in a burnout kiln before melting.
Be sure to use a rosebud (the bigger the better) for the tip.
Copper melts at around 2000 F (higher or lower depending on the
alloy) so oxy act is definately hot enough, just a question of
the total BTU output of the torch (for 400 grams you need a good
Did you use any flux? Again, pure copper is a problem and flux
might be a help (I just do not know what material to suggest).
Laastly, from the descriptions about the granules remaining in
the crucible, I would think there was a lack of heat. I melt 80
lbs of bronze with a forced air, propane burner in about 40
minutes. BUT to melt 4-5 lbs in a crucible with a hand tourch
is very difficult. Try making a kalwoll “furnace” to help retain
the heat and to heat the crucible 360 deg . Pretty easy to make
the “furnace”, a bit of wire, few sq ft. kalwool and the burner
(also home made if necessary from pipe and a hair dryer/blower).
If more instruction is needed/wanted, let me know.
Hope these thought help anyone interested.
Maiden Metals Foundry