On Aug 3, 6:36*pm, Bob Engelhardt wrote:
This is soldering flux that has powdered solder in it. *You apply it to
the joint, heat, & apply solder. *Just like you do for regular flux. *So
why use C-flux?

It's not pre-tinning, as that means wetting the joint surfaces before
assembly.

And if the C-flux isn't applied to the whole joint, the whole joint
isn't going to be wetted, just like regular solder.

The Rector Seal web site says "When heated, it reduces the surface
tension in the joint and allows the solder to flow easily and uniformly
into the joint." *Which is what regular solder does.

What am I missing?

Thanks,
Bob

I've used similar stuff for copper plumbing projects, with the various
lead-free solders around, it prevents dud joints. They're making all
sorts of different soldering alloys out there, many do NOT flow like
the old lead-tin stuff or even the somewhat newer tin-silver stuff.
Heat some of it too long and it just turns into metallic dough and
doesn't stick anything together, or flow into the joint, either.

The stuff I used could be applied, heated and no extra solder was
needed on properly fitted joints. Worked well for tinning soldering
irons, too. The key thing for pipe joints was to apply the stuff, fit
the parts together and give the tubing about a 1/4 turn before
heating.

Stan