Green Flux

BF is soldering copper pipes as I visit him in the master bathroom...

TMF pointing at the propane flame, "Oh look!  It's green."

BF, "Yep." I think he's concentrating.

TMF, "Is it a reaction between the flame and flux or something?"

BF, "Yes it is."

I'll admit I'm pretty proud of myself for even knowing the word "flux."

A few moments pass as I watch the flame while BF is working.

TMF, "What's the difference between soldering and welding?"

BF long pause, "Well...do you know what's going on right here?"

TMF laughs, "No, I have no idea what's going on!"