Plumbing sweating question

Sometimes you get lucky .

Not really. What flux is intended for is to remove oxidation and corrosion from the surface and to prevent oxidation during soldering. That will help the solder flow better but this is a side effect of a clean joint.

Steve Manes Brooklyn, NY

I soldered some 3/4" pipe and didn't like the looks of some of the joints; there were a few spots that didn't show solder and I don't want any leaks.. So I took them apart. The insides were completely tinned on both parts, so the joints were probably okay. (Is that a fair evaluation?) But after I cleaned them up they wouldn't go back together again because of the thickness of the solder. I heated them up and worked them back together, and added a little more solder. Now the joint looks fine.

Is it? I didn't use any flux the second time because it just would have fried off, but since the joint was already tinned from the first time, that shouldn't matter should it? The flux is just to get the solder to flow over the copper, so it shouldn't be necessary on tinned copper. Right?

Thanks John; people like you make the internet worthwhile.

Use a Minimag and a miror. Can you see silver all the way around, where the two parts come together? If so, you likely got it right.

If you're going at it a second time, wirebrush and then add some more flux.