Originally Posted by
unterhausen
I don't think flux has anything to do with it, but people that use this technique tend to have gas fluxers.
Isn't the flux supposed to help the filler metal flow better though? If you solder copper plumbing joints the principle is that the solder goes wherever you've put flux. This may be why duanedr's "stack" is so much flatter and more wetted in. It is a very nice looking joint and probably stronger but this may explain why it doesn't have the same bead profile.