Originally Posted by
unterhausen
There is flux in a gas fluxer?
Yes but it's not spread all over the metal. This article is quite good:
https://www.harrisproductsgroup.com/...ing-works.aspx
The filler metal is being pulled in two directions at once. It wants to make itself into a little blob but it also wants to get sucked into the parent metal. A stack of dimes is a fine balance between the two. If you cover the parent metal with flux it may make the "adhesive" force stronger compared to the "cohesive" one. The best way to find out would be to try it but I don't have a gas torch with or without an inline fluxer.