After I have soldered 14g. rings around the ends of sterling tube, I
noticed the tube has a slight brownish haze after buffing. I flux
the pieces with liquid flux. It seems to polish out but then returns.
Newbie but learning. Thank you in advance for the help you offer me.
Thank you all for all your wonderful posts!
Kathy
After I have soldered 14g. rings around the ends of sterling tube, I noticed the tube has a slight brownish haze after buffing. I flux the pieces with liquid flux. It seems to polish out but then returns. Newbie but learning. Thank you in advance for the help you offer me.
Welcome to one of Sterling silver’s most endearing and wonderful
habits. it’s called “fire stain”. Until you learn how to deal with
it, it can drive you nuts. What happens is that when heated to
annealing or soldering temperatures, silver, even though still solid,
is quite permiable to oxygen. The oxygen reacts with the copper in
the sterling silver. At the surface of the metal, this gives you
black copper oxide, which easily dissolves in pickle when done. But
deeper into the metal, you get a different, reddish, copper oxide
forming within the surface layer of the metal, and penetrating into
it to a depth dependent on how hot, and for how long, and under what
conditions, the silver was heated to. When, after soldering, you
pickle your piece, you end up with that nice dead white surface,
which is pure silver, since the copper right at the surface oxidized
and is now gone. This layer is fairly thin. When you polish the
metal, you cut through that initial white fine silver layer, and into
the layer that’s got a reddish hazy look to it. It’s not obvious
until you have something to contrast it with, against a nice polish,
so areas where you’ve cut through that layer then have a deeper,
richer silver color without the reddish/creamy haze.
Ordinary soldering flux helps some, to retard formation of fire
scale (the surface black oxide) and fire stain (the subsurface red
oxide), but it won’t totally prevent it. To prevent it you need to
coat the surface with a flux which is capable of totally excluding
oxygen from the surface of the metal, not just capable of dissolving
oxides that form (which is mostly what soldering fluxes do)
Search the Orchid archives for discussions of fire stain/fire scale,
as well as descriptions of how to mix up Prips flux, or commercial
alternatives such as cupronil flux, Firescoff, and others. Some of
these will function as an adequate soldering flux as well, though
never as actively as those fluxes formulated especially as soldering
fluxes. Often, for best results, one has to use two fluxes. One the
fire stain preventing surface coat, and the other the chosen
soldering flux used just in the joint itself. Oddly, some of the
most active and effective soldering fluxes (the white paste fluxes
like Dandix and Handy flux) seem to tend to even promote the
formation of fire stain underneath them even while wonderfully
assisting solder flow. I suspect that what actually happens is that
these very active fluxes get depleted before you’re done, and loose
effectiveness. But it could even just be that the fluxes themselves
are permiable to oxygen somehow. Not sure about that…
Anyway. Your problem is fire stain.
Have fun. It’s an adventure…
Peter Rowe
Hi Kathy,
It sounds to me like you have developed some firescale on your
tubing/bead, which is quite a challenge to remove.
What I do in this situation is to do what is sometimes called
"depletion gilding" (that is a term usually used for gold, not
silver, but the basic method is the same).
What you need to do is to raise the fine silver on the piece by
repeated heating and pickling. Basically, the acid in the pickle
eats away at the copper in the surface of sterling, leaving a very
thin fine silver layer on the outside of the piece.
To do this you need to lightly heat the bead/tubing with your torch
until it turns a light yellow/brown straw color then place it
directly into the pickle. Then after pickling, clean the piece of
what I call “pickle skin” (i.e. the hazy skin that is always left
after pickling), by lightly brushing with a soft toothbrush, and then
heat the piece again, repeating this process over and over until your
firescale is eliminated. If your firescale is deep, it can sometimes
take up to 20 times of repeating this process to get rid of it.
Truly, I have learned that the best way to deal with firescale is to
prevent it. I do this by always coating my pieces with a mixture of
denatured alcohol and boric acid before I solder. It protects the
metal well, and I have much less problems with the development of
firescale.
As you learn finesse at soldering (lots of practice); controlling
your heat well, getting the torch off the piece as soon as your
solder flows, keeping an even heat throughout the soldering process,
etc. etc. you will have less firescale issues as well. In my opinion
there is an art to soldering, and it takes time and practice, and
patience too. I love to solder, and have discovered that I am always
learning something new with each piece I make that requires some real
fine soldering techniques.
There are some great fluxes out there too, which can help reduce
firescale issues by protecting your work. Read the string on “Cracked
Solder Joints”, it has a lot of good on different
soldering fluxes. If something is really delicate, I use the
"Firescof" brand to coat my piece completely before I solder. It is
pretty expensive stuff though, so I rely on the good old fashioned
boric acid & alcohol for most things.
Good luck, and hang in there! Remember too, that we are all still
learning, no matter whether we are “Newbs” or have been at jewelry
making for years! The way I see it is, I am learning every day, and
the day I stop learning will be the day I die, as there is always
something new I learn every time I sit at m bench!
Regards,
Teresa
Dear Teresa:
Thank you so much for taking the time to answer my post! I am heading
out to the bench to give it a try - thank you for all your
Happy new year!
Kathy
Hello Teresa
It’s my first time on this Orchid conversation so I hope I do this
right.
Regarding your firescale prevention method, I’ve tried a mixture of
200 ml alcohol to 3 spoones of boric acid powder but i doesn’t
dissolve.
Do you use the same proportions?
Best Regards
Eva
Regarding your firescale prevention method, I've tried a mixture of 200 ml alcohol to 3 spoones of boric acid powder but i doesn't dissolve.
What kind of alcohol? if it is ethyl (denatured or pure ethanol)
then you will not get much boric acid into solution. Methyl is much
better at dissolving the boric acid but is quite a bit more toxic so
greater care needs to be used when handling methyl alcohol.
Alcohol-boric acid fire coat works well for gold but is not nearly
so good on sterling. The silver is just too good at absorbing oxygen.
A better fire coat for sterling is one of the varaitions on Prip’s
flux (either home made or off the shelf like Prip’s from Griffen or
Cupronil or Rio’s Stop-Ox II
Prips’s Flux
2 oz borax
2 oz trisodium phosphate (TSP)
3 oz boric acid
1 qt water
Boil chemicals and water allow to cool. put in spray bottle or
airbrush and spray onto work that is warmed to the point of the flux
drying instantly when it hits the surface. Cover the whole surface
of the work. If soldering then while the work is still quite warm
apply a tiny and I mean very small amount of either paste or liquid
soldering flux right at the joint. It should also dry instantly if
done properly. Then heat for annealing or soldering as normal. Apply
solder with the pick method for best results.
James Binnion
James Binnion Metal Arts
Hey Eva,
You know, I have never really “measured” how much boric acid I use.
This is a habit I picked up in school, and probably a bad one (as I
am sure many Orchid-landers will tell me, LOL) Where I went through
my metalsmithing, a University in Ohio, we had a plastic mayonnaise
jar that sat (and still sits) inside a rectangular glass Pyrex dish.
Inside that jar we kept our denatured alcohol filled at least 2/3
full, and added the boric acid as needed, sometimes up to 1/4 or 1/3
cup of the boric acid powder would be added, even if there was
solidified boric on the bottom of the jar. Often the boric acid does
start to solidify in the bottom and we would turn the large paint
brush (that also lived there) upside down to break it up and get the
boric acid loose and mixed. There was no real recipe, and this may be
wrong, but it always seemed to work if we stirred it well and made
sure there was plenty of boric floating around in the liquid.
(grainy, yes, but it comes right off in the pickle) My professor
never seemed to have any issues with this, and he used it plenty
himself before he soldered things. We had a large and very busy
studio, often with all 6 soldering stations being used
simultaneously all day long, so that jar sees a lot of students visit
it all day.
I seemed to have picked up the same habit here in my home studio,
with the exception that I keep the lid tightly closed so I do not
always have to replace the denatured alcohol due to its rapid drying.
Use of a Pyrex dish to hold your jar of mixture is an added plus
because you can prop your pieces up against the side of the dish and
coat them well, then let them dry there before taking them over to
solder. (BTW, ALWAYS store the mixture in a place that is NOT close
to your solder area; HUGE fire hazard if it were to spill where you
are soldering!!) Then the dried boric that always builds up on the
bottom of the Pyrex does not make a mess and is easily recycled by
just scraping it off the bottom of the dish and dumping it back into
the jar of alcohol. I DO always try to grind my powder finely by hand
with my mortar and pestal, but it tends to still get grainy, and I
ignore it as everyone else did in school.
I did seem to read a recent string about the use boric in denatured
alcohol that commented about what mixture was best and the least
grainy??? You might try looking back a little, or running a search. I
think it was comments made in a string about fluxes, or cracked
solder joints? I cannot remember, as I just breezed through it. But,
good luck. I wish I could give you a better answer on the recipe, but
it seems to me if there is boric floating in the solution, that there
has to be enough that dissolved?? It always was enough to satisfy our
"Distinguished Professor of the Arts", hehe, and he is a master
metalsmith and a real MASTER at soldering too.
Happy Solder & Hammering!
Teresa
Thanks James for the recipe for Prips! I have made note of it and
will have to try this stuff out. I have wondered what it was made of,
and was told in a workshop given by Michael Boyd that it works
beautifully, as well or better than Firescoff, but never have seen
the recipe before. I appreciate the tip!
Teresa
Thank you James Binnion, for the concise description of using
homemade Prips solution. Put ting this on a 3 by 5 card and posting
in my little shop for my eyes to review every time I solder.
Hi all,
Unfortunately I have not been following this thread too closely and
missed James Binnion’s comments on making your own flux. Also my
attempts at finding it online have not been successful so far.
Could someone repost it or send me a link?
Thanks a ton!
John Dyer