I'd like to remove some old copper flashing to repair the rotting wood beneath it. My plan was to de-solder the old flashing joint (I'd like to reuse the flashing when done). So I bought a used copper hand iron and heated it for half an hour with a propane torch. Before hand I cleaned the joint with steel wood and ruby fluid. I also cleaned the iron and with ruby fluid before and after heating it and tinned the iron. But the hot iron didn't make a mark on the old solder.
Does anyone know how long I need to heat it to get it hot enough and how to tell when it's hot enough (glowing red?). Or is there another way to remove the flashing without destroying it? I'm concerned that using an angle grinder would be too delicate a job and there are some places it probably wouldn't fit.