Quick question about flux removal. I use Gas Flux brand fluxes on my frames along with the Gas Flux liquid system mainly because that is the way I was taught and haven't tried other brands. Their fluxes are supposed to wash off with warm water and most of it does, the silver-brazing flux always comes off easy but the flux that I use for brass/bronze always seems to leave a few hard spots that I have to file off or chip off, mainly around the BB shell. I imagine its from the heat but it is not burned up, just clear and hardened like ice. Any advice out there, any solutions to use that work well? I don't have a soaking tank, only a large sink or bathtub, but I would get one if it would make a difference.
Soak over night is what I recommend. Using a heater in the water is also good. Flux is acid and needs to be removed. Those hard chunks on the outside the tubes are also inside the tubes as well (too a lesser extent of course) so mechanical flux removal from the outside is not good enough - you need water to get inside the tubes to get all that stuff off otherwise you can have corrosion attacking the joints from the inside out.
Becareful buying/selling bike parts on-line. I learned the hard way. :(