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Inconsistent polishing results

I have been getting inconsistent results lately polishing silver. I
am getting a mottled look after the final polish, i.e., part of the
piece is mirror finish and part even though highly polish looks
unfinished. I did read the recent submissions on polishing and have
tried various compounds and buffs but am still having this problem.
Thanks for any advice to cure this problem.

Wanda

Wanda, You did not mention if you are soldering the pieces before
polishing. If you are soldering without a firescale preventative
coating you are getting firescale. Firescale shows up as a purple or
copper haze on polished silver. Its formed by oxygen combining with
the copper in sterling silver.

Several Companies sell firescale preventative fluxes. They are
painted or sprayed on the silver before soldering. There is also a
homemade product called Prips. You might want to try one of these
products.

Lee Epperson

Wanda,

This sounds like the metal was over heated and /or not Pickled
properly.

When this happens you can get white or frosty blotches in the metal
that will not polish out.

Greg DeMark
email: greg@demarkjewelry.com
Website: www.demarkjewelry.com
Custom Jewelry - Handmade Jewelry - Antique Jewelry

Hello Wanda,

You say you “…have been getting inconsistent results lately
polishing silver. I am getting a mottled look after the final
polish, i.e., part of the piece is mirror finish and part even
though highly polish looks unfinished.”

If the pieces have been soldered, it sounds like the Dreaded Fire
Scale to me. Prip’s flux to the rescue. If there has been no
soldering, what kind of heat or chemical process might have been
used - more info is needed.

Judy in Kansas, where winter is really here - nights in the 'teens.
and many thirsty birds at the waterer!

Hello;

Take a real close look under magnification, it just may be
micro-porosity! If so, you will have to burnish the surface and
then polish.

Pat DIACCA Topp

I agree with Judy in Kansas…sounds more like fire scale to me than
porosity as someone suggested. Hard to tell though without seeing
it.

If it is you have three choices…sand it out, polish it out or burn
it off with a solution of 50/50 water to nitric acid. The first two
will result in serious loss of valuable metal not to mention a
possible change to the landscape of the piece, while the latter can
be nasty stuff to use. If you do use the nitric, do it out doors
and wear proper protection. When you put the piece in, warm it first
and then only leave it in the solution for about 15 secs as it will
etch away the metal. It might take a couple of dippings to get rid of
the scale. You can also try to deplete guilde it by heating and
dropping it directly into pickle four or five times. Problem with
that is it simply brings a layer of pure silver to the surface and
you must be careful when polishing because the layer can be polished
away.

Good luck and cheers from Don at The Charles Belle Studio in SOFL
where simple elegance IS fine jewelry! @coralnut2

Wanda

The problem may be the steps that you are taking before you start
polishing. I generally sand my pieces with successively finer grits
of sand paper, stopping at #600. I know that there are many out there
that sand down to 1500 grit before polishing. I start with tripole
and finish off with green rouge. I get great results on sterling
silver as well as gold

Regards
Milt Fischbein
Calgary Canada

Thanks to all who responded to my initial inquiry regarding
inconsistent polishing results. Based on your responses, I believe
I am dealing with firescale and overheating. I use “Handy Flux” for
my soldering application and coat my pieces thoroughly before
soldering.

My next question. Can I get rid of the firescale on these pieces or
do I have to scrap?

Wanda

Hello Wanda,

You should be able to buff through the firescale - ZAM is good. If
the firescale is deep you’ll lose metal. Give it a try; nothing to
lose and you might not have to polish a whole lot to eliminate those
grayish stains.

The real question to solve is why you get it if you have a good flux
cover. Even a nice thick flux doesn’t hold up forever, so maybe
you need to evaluate your soldering technique. Be sure to heat the
whole piece evenly. Perhaps adjust your torch to give a slightly
hotter flame. Get in and out more quickly.

Peter Rowe, advice here? Your knowledge has certainly helped me in
the past.

Judy in Kansas

Hi Judy,

Firescale will form under paste flux and other fluxes not designed
to prevent firescale.

Try covering a piece of silver with one of the anit-firescale
fluxes and drop a touch of paste flux in the middle of the piece.
Heat to solder temperature and polish. You will have a very well
defined spot of firescale where the paste flux was. That’s the
reason anit-firescale fluxes were developed.

Lee Epperson

Wanda,

I get the digest, so I’m always a bit late and you’ll have heard this
by now, but for heaven’s sake, don’t scrap your work just because of
a little firescale! I think I’d have thrown away about half of the
stuff I’d done if that were the case.

Firescale just means that finishing will take a bit longer - if it’s
in an area that can be treated in such a manner, sand off the
outermost layer of the piece with sanding sticks or discs and
repolish. You should be able to see whether the firescale is gone
when you reach the tripoli stage. If it’s still there, hit it again
with the sandpaper. I find it usually doesn’t take much sanding to
get rid of it.

On highly contoured or textured pieces, you might take the opposite
approach and try to cover the whole piece evenly with firescale.
This will give it a greyer appearance than usual, but this is not
always unattractive - on an oxidized, “baroque” piece, it can
actually add to the overall finish.

You can also heat and pickle the piece to raise a layer of fine
silver - just be careful not to polish through it. I’ve only
succeeded in using this technique by accident (really happy
accident), so any finer tips that y’all could share would be
appreciated!

Cheers,
Jessee Smith
www.silverspotstudio.com

Jessie,

Do you always use one of the anti-firescale fluxes when you solder?
Properly protected projects should not get firescale.

Firescale covered areas will darken, over a period of time, faster
then non firescale covered areas.

There are two ways a project that is properly covered with
anti-firescale flux might get firescale:

  1. Paste flux or one of the non anti-firescale fluxes washes
    away the coating of anti-firescale flux.

  2. The solder temperature is maintained for too long a period of
    time on a project covered with anti-firescale flux. All fluxes
    will break down after a lone heating cycle. It is best to break
    solder operations into several steps rather that try to
    accomplish too much in one solder step.

Always cover all the surfaces of a project with an anti-firescale
flux before soldering. In many cases it is best to pre-polish areas
before soldering on findings.

There is a way to prevent firescale from forming on vacuum cast
items. The process is very simple and cost nothing. For a free paper
on the process contact me off line. I will send you a paper I
prepared on the subject.

Lee Epperson

Lee,

I’ve not had too much trouble with firescale since learning to use
boric acid and alcohol firecoat. As I think I mentioned in a
previous post, I originally learned to solder using only Handy Flux,
which resulted in a lot of firescale headaches.

I’ve rarely had trouble with firescale on any of my cast pieces,
probably because I generally design them so that they require
minimal soldering operations, or better yet, none! :wink: Thanks for
the offer of assistance, though.

Cheers,
Jessee Smith
www.silverspotstudio.com