max time between applying flux and soldering

I have let them sit for days, no problem.....

Not sure on this one, but I flux them as soon as they are cleaned and then it doesn't matter. After all, most of what you are cleaning off is oxidation.....

Good luck with it.....

Jeff

You don't want any visible oxidation. If things are not bright and shiney, you need to clean them. I think when you have sanded the pipe that is the time to put on the flux. Better to have cleaned and fluxed several days ago, than to clean several days ago and then flux just before soldering.

Dan

Strange. If the tank appears to be half full, I'd look elsewhere for the problem. Unless it's killer cold, as long as you draw from the tank, it should continue to produce, at least enough to keep your flame going. Have you checked your torch for obstructions?

If you haven't noticed, flux begins working when you apply it. Check it out next time. Even shiny, well cleaned fittings and pipe undergo a slight color change as you apply the flux. It's already reducing the oxides, it doesn't have to be heated. As others have stated, as long as the flux is present, you should be able to heat and solder, assuming the flux hasn't turned dark green on you. At that point you might want to dismantle, wipe down, and start over.

Good luck!

Harold

The fluxed joints shouldn't deteriorate at all. They should behave the same as if you had just fluxed them.

This depends entirely on the flux. All fluxes should _prevent_ the joint oxidising when its being soldered (assuming you don't burn it, of course), but not all of them are able to _remove_ oxide that was already present. Some fluxes are more active than others; the more active the flux the better it is at removing oxides. The usual resin fluxes are not particularly active at all. Its generally best to remove oxide before applying the flux.