First of all, many thanks to those who helped me (and challenged me
thanks Leonid) with the Oval gypsy setting. I tried it and it
worked… also for the enlightenment on annealing Sterling. Next
question - if I may - concerns firescale. I have read several
articles and know to be wary of it, pickle and flux. I have made
several pieces in Sterling that have exhibited a kind of “stain”,
which only becomes apparent after buffing (last stage) with rouge.
The marks look more like ingrained rouge than something subsurface.
They do take a lot of repolishing (with a grit impreg rubber wheel)
to remove. My question, naive though it may be, am I dealing with
"firescale’ or just buffing incorrectly ? I do know that it takes
almost as long to remove the stain than it does to make the piece…
Sounds like the dreaded firescale to me. Is it a bit dark
purplish/brown? It is a devil to remove and yes, it usually takes
more work to remove it then creating entire piece combined.
My first question is how did you make the projects you are
describing.
Fire scale will form on sterling if the metal is not protected
during soldering. There are several anti fire scale fluxes on the
market that will prevent fire scale from forming during soldering.
Some better than others.
There is even an anti fire scale flux you can create on your own. A
review of the Orchid Archives will lead you to the formula.
Before each solder step the metal should be totally coated with the
anti fire scale flux.
Fire scale is a sever problem on castings. Fire scale forms as long
as sterling is heated above about 100 degrees F. During casting
sterling is maintained above 1000 degrees for a long period of time.
Fire scale forms continually during that time.
There is a process listed in the Orchid Archives that will prevent
fire scale during vacuum casting.
THE BEST IDEA IS TO NOT LET FIRE SCALE FORM. Once fire scale forms
you can remove by a braiding it away with course polishing compounds
or abrasive wheels. Unfortunately they can remove design. There are
chemical processes for removing fire scale that I would not
recommend.
It certainly sounds like fire-stain and once there, there is no
other solution than to polish it out. Some people say you have to go
back to a coarse emery paper, others say that you should use pumice
powder. You need to find what works for you.
The trick is to avoid the firestain in the first place. You can use
a resistant alloy (like Brilliante in the UK), plenty of flux
(perhaps using the flux mixed with meths then applied and warmed to
leave a fine coating). A reducing flame always helps, so if I have a
large piece to solder, I will sometimes use 2 torches. One with a
large bushy flame, the other with a fine concentrated flame. Anything
to keep the oxygen off the surface.
Also, you can try to surface enrich the piece first by heating to
black hot and then plunging in a weak sulpuric acid or safety pickle.
This is supposed to disolve the copper out of the alloy near the
surface.
You are describing firestain or firescale. Instead of struggling to
remove it, prevent it. Make up some Prip’s flux or buy some flux
that is advertised to prevent firescale.
Prip’s is inexpensive to make and lasts a very long time. There is
an extensive thread in the Orchid archives including the
recipe/formula and the best means to apply it. What ever type of flux
you choose, the trick is to get an even, complete coating on your
piece before you start soldering.
You should spray the whole piece of silver with Pripps Flux or
Batterns or the like until no part of the silver is exposed to air.
The surface should be warm when you spray it so it will turn white
frosty looking. That will keep the firescale away. Check the archives
and you can find some really useful info about firescale and flux.
You can use Argentium and never worry about firescale ever. That is
what I do. =)
It certainly sounds like fire-stain and once there, there is no
other solution than to polish it out.
To get rid of fire scale I switch between bobbing compound and Zam.
I use the Zam to identify where the fire stain is at then hit it with
the bobbing compound. Once most of the firescale is off I finish up
with Zam. It does a pretty good job on small spots of firescale and
puts a nice polish on silver.
Rick Copeland
Silversmith and Lapidary Artisan
Rocky Mountain Wonders
Colorado Springs, Colorado rockymountainwonders.com
I’ve noticed, on some silver jewelry I’ve polished for customers,
that some jewelers just leave firescale on their pieces and simply
don’t worry about it.
And while firescale is a major PIA, I can understand leaving it
there since, unless silver jewelry is highly polished, one cannot see
firescale anyway.
I had a friend who was learning how to make jewelry and she asked
what firescale was because she’d never seen it. Turns out she was
using tripoli but not rouge and so never had her pieces shiny enough
to spot it.