Until recently I had been using a spray bottle to apply Gesswein’s
Dr. Frank’s Fabulous Flux to protect against firestain. The problem
was, when applying liquid flux with a sprayer, the large droplets
would produce voids on the object’s surface which would have to be
resprayed. The flux would also build up a thickness that would
occasionally bubble off solder pallions.
Recently, when visiting a local hobby shop, I noticed a number of
airbrushes in their display case. For years I had contemplated using
one as an applicator, but didn’t want to spend the money. However,
next to the professional airbrushes I saw a $28 Badger 250-4
airbrush with a four-ounce reservoir that I couldn’t pass up - it was
worth an experiment. I also purchased a $5 brass accessory that
allowed me to connect the airbrush to my air compressor. I raced
home, excited at the prospect that this inexpensive, elegant solution
would solve my flux issues.
I found that the airbrush assists in depositing a finer, even layer
of flux, and eliminating the bubbling that would normally occur if
applied by brush or mist sprayer. There is also a volume adjustment.
And the lack of bubbling flux keeps pallions in place. Also, since
most liquid flux evaporates with this applicator almost immediately
after applied to a torch-warmed object, there are no voids left on
the surface to have to re-spray. This method puts flux just where you
need it, reducing waste. The airbrush should work well with other
liquid, non-flammable fluxes.