[Noisebridge-discuss] soldering copper sheet metal

[jim]

     I've soldered electronics and plumbing and
am stuck trying to solder copper sheet metal.
I've used a soldering iron and a propane torch.
I've used alcohol, acetone, and paint thinner
to clean the copper as well as fine and coarse
sandpaper to clean the surfaces. I'm using
electronic flux (haven't yet tried plumbing
flux).
     The soldering is not working: solder does
not flow or adhere to the copper, and there's
a brown residue that appears after heating.
Using a torch for forty or fifty seconds
results in flame that does not immediately
expire.

     Anybody got tips?