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Coating to prevent fire scale on 18K

#1

I’m on the road at the moment, and was making wire for a project
when I realized that I had no boric acid handy. I normally coat my
wire in that to prevent scale, so I was pretty bummed out that I’d
forgotten to bring it with me.

Looked at the flux (the green stuff from Rio) and thought, “Hey, why
not?” I diluted some of it in some water and soaked the coil (18K
yellow wire) in it, then annealed it. No scale.

So… is there any reason not to do this? Been using boric acid in
alcohol for years, because that’s what I was taught, but this seems
pretty effective, maybe even more so.

Loren
golden-knots.com

#2 
So... is there any reason not to do this? Been using boric acid in
alcohol for years, because that's what I was taught, but this
seems pretty effective, maybe even more so.

Sure it works. The flux is more active than just the boric acid, so
it will tend to burn off more quickly if you heat for too long, but
for just annealing, that’s unlikely. The main problems are that the
flux generally costs more than just boric acid (a minor
consideration, as both are cheap), and more importantly, the alcohol
boric acid solution wets the metal, and coats it uniformly. The water
based flux tends, due to surface tension if not absolutely clean, to
not wet the whole surface, instead balling up/pulling away from
areas. You get around that by brushing more on while it’s hot enough
to keep it there, but that’s more work. So while the flux works fine,
in general, the boric acid/alcohol mix may be a bit more reliable and
foolproof. But YMMV, as always.

Peter

#3

A tried and true product is Cupronil made by 4S labs- great as a
firecoat and flux portable, sprays reliably every time.Forerunner to
Firescoff ( which I am less than impressed with at best). The “green
stuff” is a self-pickling, flux, which means it contains
hydrochloric acid ( which gives these types of fluxes their neon
colour) so it “cleans” the metal as long as you don’t keep the flame
trained on the join too long, etc…eliminating the need for pickling
in higher karat golds- Any higher karat golds though are less prone
to firescale than alloys with a higher percentage of copper as its
the copper in the alloy that helps set up perfect chemical reaction
for the formation of cupric oxides, or firescale/firestain - whatever
you want to call it.The more over heated the piece is the deeper the
firestain will be, so hit and run soldering operations on 18 kt and
above gold will leave little if any problem regardless of the
preventative coating you use…rer

#4

Firescoff a was a waste of money, just did not work!

Richard