Back to Ganoksin | FAQ | Contact

Firestain


#1

I’m mainly a goldsmith, but I work alot in silver as well.
Unless you really like to polish on a big machine with lots of
tripoli, firescale is a losing battle, especially if you’re in it
to make money. I finally broke down and bought a flow-through
tumbler and it gives the silver a pretty decent finish above the
firescale layer.<<

Wendy,
You can get rid of firestain by using a reverse plating process.
Set up the plating so that silver is taken away from your work
so that silver is deposited onto something from which it can be
retrieved later. Firestain gone, surface ready to polish!

Richard Whitehouse.


#2

Firestain ( Firescale, or whatever one calls it . . .) usually
appears on Sterling Silver . . . it looks like grey bloches . . .
one can polish, polish and polish and these bloches will still
not vanish! It’s a pain!!!

Hi,

That most probably is subsurface oxidation. Silver can dissolve
quite a lot of oxigen when heated, so does copper. This way the
oxigen is able to oxidize the copper deep inside the workpiece,
and there is no way to get rid of this oxidation, pickle will
only act on the surface.

To prevent, it is best to cover the workpiece with a white paste
flux, boric acid is not very good, as it has too high a working
range for silver solders or easy gold solders. With boric acid
which turns into borium trioxide at 500 C, metal oxides are
changed to metaborates, and these will not move away from the
place they form, to give access for new boriumtrioxide, below
900 C. You’d have to replace the boric acid with flux at the
joint.

Silversmiths who make vessels use borax junk to make a thick
paste.

regards, Markus


#3
Silversmiths who make vessels use borax junk to make a thick
paste.

Markus
Could you explain what borax junk is. I do a lot of overlay with
silver and fire stain is a big problem with this process.
Thanks Jim Blumer


#4
 Could you explain what borax junk is.  I do a lot of overlay
with silver and fire stain is a big problem with this process.

Borax . . . that’s the stuff which is supposed to be in mostly
all fluxes . . . Denatured Alcohol and BORAX (20 mule team???)


#5

I see this subject come up frequently and working mostly in
silver I use Pripps Flux. The recipe is in THE COMPLETE
METALSMITH. NOthing works 100% and I’m starting to agree with
someone who said they don’t protect their pieces at all and
settle for a brass brushed finish on the fine silver coating from
pickling. Pripps helps for a few solderings but if you do as many
solderings as I do on some pieces you get used to working with
heavier guage silver and then polishing it down to get rid of
firescale afterwards…Dave


#6

I just looked at the label on the flux I use and it contains
"complex flouroborates" which is probably related to Borax in
some. The flux is JM Easy Flo, it does have a tendency to reduce
firestain around the joint because it turns into a liquid at
soldering temperature. Richard W UK


#7
I see this subject come up frequently and working mostly in
silver I use Pripps Flux. The recipe is in THE COMPLETE
METALSMITH. NOthing works 100%......

G’day; to save you the bother of looking it up:-

PRIPPS FLUX
Borax (Sodium diborate) 30g
di-Sodium Hydrogen Phosphate (Na2HPO4) 30g
Boric Acid 44g
Water to 500mls

Your local pharmacist will make it up for you for a small fee.
It isn’t really very poisonous, but don’t try drinking it - it
doesn’t taste a bit like Coca Cola. (which also contains
phosphate) Pripps Flux does help but I agree with Dave S;
nothing will completely eliminate fire stain other than not
keeping your sterling or low carat gold hot for any longer than
you can help, which means working very quickly and hoping nothing
goes wrong - but keep Murphy’s Law in mind; if it CAN go wrong it
WILL. In this context, hot means any temperature above when your
work can just be seen in the dark - about 650C - 700C. Fine or
pure silver doesn’t get firestained because there’s no copper in
it, but it’s too soft except for jewellery which isn’t going to
get much everyday abrasion. The liquid containing alcohol which
(Nina, I think) wrote about is meth spirits saturated with boric
acid. Use a flat plastic container with an airtight lid, put
some boric acid in it - just some - and pourin the meth’s. Shake
well (you’ll see if the container is airtight!) and simply dip
the work into it, take it out, CLOSE THE CONTAINER!, and set fire
to the work. It will have a thin coating of boric acid over it,
but unless you work fast, your job will still get firestained.
And that’s the best we can do for you. But Cheers, –

        /\
       / /    John Burgess, 
      / /
     / //\    @John_Burgess2
    / / \ \
   / (___) \
  (_________)

#8

Could you explain what borax junk is.

Hi Jim,

Borax junk is borax in a solid form, usually sold as a truncated
cone, 3�" long with 1�" dia thick end. You prepare your flux by
grinding it in a flat dish with a roughened bottom, adding a
little hot water. So you can make a thick paste to cover the
item to be annealed or soldered (with an ordinary paint brush).
At a soldering joint you’d best use a ready made commercial
flux.

regards, Markus


#9
 I just looked at the label on the flux I use and it contains
"complex flouroborates" which is probably related to Borax in
some. The flux is JM Easy Flo, it does have a tendency to
reduce firestain around the joint because it turns into a
liquid at soldering temperature. Richard W UK 

I use BATTERINS (sp???) IT cleans, and reduces fire scale . .
. but, the fire scale still shows up (they tell me I should use
a lot of of the stuff, but then everything I try to solder,
“floates” and doesn’t settle in the proper place!!! Do you
also have that problem???


#10

PRIPPS FLUX
Borax (Sodium diborate) 30g
di-Sodium Hydrogen Phosphate (Na2HPO4) 30g
Boric Acid 44g
Water to 500mls

In the US the recipe calls for TSP (TRI-sodium phosphate, though
they probably both work). If you buy TSP in a hardware store
you’re getting something that isn’t TSP as its not eco-friendly
in some states. The solution is to go to your local home brew
store as TSP is commonly sold there to clean out beer bottles
before rebottling. Just a tip. I use Pripps alot and it does
save some labor. Another tip is to buy an artist’s mouth atomizer
at most local art supply stores. Its about the only thing that
will spray that stuff well and not clog up, a tip from Peter
Rowe…Dave
http://www.opendoor.com/stephensdesign/crystalguy.html Crystalguy
Art Jewelry, Magical Art Jewelry for the Enlightened Mind


#11

Yes I do have the same problem with very small pieces of solder
that seem to have a mind of their own and wander all over the
place. We call small pieces of solder Pallions. I just have to
push them into position until they melt. Richard W UK


#12

Yes I do have the same problem with very small pieces of solder
that seem to have a mind of their own and wander all over the
place. We call small pieces of solder Pallions. I just have to
push them into position until they melt. Richard W UK

Richard,

If you preheat the piece, dip the pallion in flux and place it
where your want it, the hot metal will turn the flux into instant
adhesive, and your solder stays where you put it.

Try it, I think you’ll like it.

Have a great day.

Sharon Ziemek


#13

If you melt the flux first, the solder doesn’t move around so
much.

Marilyn Smith


#14

We all agree that firestain is a pain in the butt. I have used a
MIG welder from time to time. There is an Argon gas shield
around thew steel welding wire to prevent the atmosphere
oxidising the weld. It also prevents the need for flux. I wonder
why a manufacturer for the jewellery/silver trade has not come
up with the same idea. The use of an Argon shield would prevent
oxidation and firestain. Any suggestions? Richard W UK


#15

We all agree that firestain is a pain in the butt. I have used a
MIG welder from time to time. There is an Argon gas shield
around thew steel welding wire to prevent the atmosphere
oxidising the weld. It also prevents the need for flux. I wonder
why a manufacturer for the jewellery/silver trade has not come
up with the same idea. The use of an Argon shield would prevent
oxidation and firestain. Any suggestions? Richard W UK

Some casting systems use an inert gas to reduce the oxidation
during the melting process.

Don’t have much problem with high karat gold alloys- but is is
real annoying when working in sterling.

Rick
Richard D. Hamilton

Fabricated 14k, 18k, and platinum Jewelry
wax carving, modelmaking, jewelry photography

http://www.rick-hamilton.com
@rick_hamilton


#16

Does anyone use a small electric kiln for soldering many items
at one time? Someone recently told me she uses an electric
ceramic kiln for this purpose, and is very happy with the
results. She oxidizes and rough polishes her line, so the subject
of firescale didn’t come up. I was wondering if it would be more
of a problem. Does anyone know what kiln would work?

Also, I need to find or make a tie clip- I have used the small
one from Toback, but now need one without teeth, that would still
hold fabric securely. It can’t have teeth because it is used to
hold silks, and other rather roughly woven fabrics, and the ones
with teeth snag the threads.

Thanks, Ruth


#17

Fishbre,

Yes, borax is the ingredient in several fluxes, and the borax in
Twenty Mule Team laundry borax works, too. I usually grind it a
bit in a mortar and pestle before dissolving it in alcohol for
use. It tends to dissolve faster and to dry leaving a smoother
film on the piece after being ground. This, by the way, also
helps keep some stones (like cz) from being damaged by thermal
shock while retipping, etc. Metalsmth


#18

Hi Ruth,

Does anyone know what kiln would work?>>

Any kiln that will get up to the melting point of the solder
your using will work. In industry they use soldering ovens with
moving belts & some with inert gas atmospheres. The unsoldered
pieces go in on 1 side & solder pieces come out the other, sorta
like some pizza ovens.

It can't have teeth because it is used to hold silks, and other
rather roughly woven fabrics<<

Why not grind the teeh off & with a little forming adjustment
(bend it) you’ve restored the tension & are back in business.

Dave


#19

Foxymom,

Good thing I don’t feel like doing my homework. It gives me time
to play on the gray monster.

I once tried to solder in the kiln. No good results for me. What I
have done in the past is use the kiln to preheat large pieces
that are jigged so they can be moved in and out of the kiln. I
preheat to 1200 degrees F and remove the piece to a safe place
like a waiting firebrick and complete the soldering as fast as I
can with the torch.

Have heard of people using a trivet type kiln and soldering
while the piece is cooking on the heating element.

I enamel in the kiln. Just getting things in and out of the kiln
can be a scorching chore. Lost a three week effort recently
answering the phone while enameling. Cried for weeks and spent
hours cleaning up the kiln.

Bill
Ginkgo Designs
@WILLIAM_I_EISENBERG


#20

Ruth:

Every tie clip I ever had (a loong time ago) had teeth and they
never marred the ties. If the teeth are sharp, you are a
jeweler, smooth them out (sandpaper, “evil blue wheel”, etc.).