"Tom Quackenbush" wrote in message
...

I may try again, placing the solder samples on a cleaned & fluxed
piece of copper this time. I'll pick up some 63/37 solder to try, as
well. I don't think my toaster oven is capable of reaching the
liquidus temperature of the 50/50 solder, though.

Be aware that if you place the solder on copper, or on any other metal with
which it will amalgamate, and if you heat it slowly, you will wind up with
intermetallic compounds in the solder that will keep raising its melting
temperature as your experiment proceeds.

This is the principle of "transistional" soldering, which is used in some
industries to produce higher-temperature joints than the solder itself would
indicate. Anyone who has de-soldered big joints on copper wire, especially
those that were overheated, has likely encountered this phenomenon.

Ed Huntress