and it's great stuff, but when it comes to larger silversmithing
scale pieces, it 's hard to get the spray into certain awkward
spaces and also takes sooo much blowing. It would be such a boon if
it could just be brushed on.
Kay, if you’re need is for fire stain protection during annealing,
and not with soldering, such as is often the case when
silversmithing, where one needs to anneal frequently, you should
investigate a concoction mixed up by the late Richard Thomas while he
was at Cranbrook, to solve this very question. Unlike Prips, which
uses both boric acid and borax, this mix, which he called
“ring-a-ding” (after that bell going off in your head when you
suddenly find an answer to a question). It’s got two components.
One is boric acid. And the other is a high tech surfactant. Plain
boric acid is known to be effective for preventing fire scale when
used on gold (boric acid and alcohol is a jewelers standard, after
all), but has problems with silver because it doesn’t adhere, and
pulls away from the surface on heating. Ring-a-ding solves this
with the surfactant, a material called Aerosol OT-solid, which acts to
keep the boric acid as it heats up, wetting the silver surface. The
mix is used by just dipping the work in it, or brushing it on. After
annealing, the surface is not quite as bright as is the case with
prips, but ends up slightly dusty looking, but you will not have the
formation of fire stain or fire scale. It acts, for reasons I don’t
know, as almost an anti flux for soldering, so if you use it in
conjunction with soldering operations, you have to be careful to
keep it away from the joints, or the solder will not flow well there.
As with prips flux, ring-a-ding is a home brew concoction, and due
to the need for the surfactant, a bit more bother to make, as that’s
not an everyday material. Metalsmith magazine published the recipe a
number of years ago (ten or fifteen?), and others here on Orchid may
know it as well. There may even be some firms who now make it. At
one time, C.R.Hill in Detroit mixed it up (They’re just down the road
from Cranbrook), but even Richard Thomas was not happy with the way
they mixed it (too dilute, as a liquid, rather than a slurry), and my
own single purchase of their version, back in the early 80s, also
suggested that they’d got it wrong. Not sure if they still try to
make it. We had it available routinely, to students, when I was in
college and grad school, so I know several schools provide it in the
studios. So someone out there knows the recipe… It does solve the
problem of easy application, and works reasonably well so long as you
can tolerate a slight loss of surface polish, which obviously is not
an issue when you’re just going back to hammering on a piece of
metal.
cheers
Peter Rowe