DIYbanter - Melting brass and bronze for casting

"Mike Firth" wrote in message
...
I "know" that holding brass or bronze at high temp burns off the low
melting zinc, tin, and lead and it is not recommended that brass or bronze
scrap be melted into ingots per one site I checked out.

[You have no idea what's in the scrap you're melting. You'll get ingots,
sure, but of what? And what would you be breathing?]

None the less
1. Is it better (more consistant results) to bring the first batch of
metal up from cold or to heat the crucible and furnace to near the final
melt temp and add the metal at that time?

[Start with all the metal in the pot. Throwing cold metal into a hot pot can
be dangerous.]

2. If it is desired to add tin to bronze or zinc to brass, how and when
should this be done? Pellets or other bits of low melt metal to molten
alloy? Cold mixing bits of both ingredients and heat mix? Lower temp
metal
melted and higher temp added?

[Melt the lowest-melting component first, with a reducing flame and under a
flux coat, and add the higher-melting ingredient to that. Make sure it's
heated enough to drive off any absorbed water before you do this. The copper
will dissolve into the tin or zinc as it gets hot enough.]

My basic stock at this point is surplus keys and what I am making is
goblet stems to blow glass into and molds and tools.
http://users.ticnet.com/mikefirth/castgobl.htm#CASTGOB

[If you're doing this for an actual use, and not just as an experiment, use
metal of a known composition. Even if you had good results with your mixed
keys (unlikely though that is), it would be hard to duplicate with the next
batch. If you want to make your own alloy, start with pure tin or zinc (or
silicon), and heavy-gauge bare copper wire. Wire is generally
electrolytically pure copper. Keys can be any alloy of brass, bronze,
aluminum, steel, or beryllium copper (which you don't want to mess with) -
recycle them some other way. Here's a good article on alloying metal in the
small shop: http://www.apecs.com.au/alloyinginsmal/alloying.htm . Here in
the US, most art foundries prefer to work with silicon bronze, because it
melts cleanly, doesn't fume, welds well, is strong and corrosion resistant.
You can buy it in ingot form all ready to go...]

--
Mike Firth
Hot Glass Bits Furnace Working Website
http://users.ticnet.com/mikefirth/hotbit46.htm Latest notes

[Hey, I've got a bin of broken glass - window glass, beer bottles, some
pyrex and odd bits of stained glass - can I melt it all together and make
beautiful art?]

Andrew Werby
www.unitedartworks.com