> Make sure you're not using "acid core solder". That will fuck your stuff up. I'm not sure why they even make that.
It's made for sweating copper tubing using a torch. I wonder if the extra heat from the torch does something to neutralize the acid because a properly sweated connection lasts forever.
EDIT: I guess this is why you are supposed to wipe the connection with a wet rag after the solder solidifies - to get rid of the remaining acid. I always thought that was done so as not to burn the shit out of someone who accidentally touched it.
EDIT 2: I don't think the solder that I have for copper tubing has any core at all. You just flux the joint first.