Personally, I don’t think that a kiln would work for soldering
to avoid firestain. It’s the oxygen in the air which causes
firstain when the silver is heated. It reacts with the copper
which then oxidises. If it were possible to solder in an oxygen
free atmosphere, perhaps that would solve the problem. Richard W
UK
Personally, I don't think that a kiln would work for soldering to avoid firestain. It's the oxygen in the air which causes firstain when the silver is heated. It reacts with the copper which then oxidises. If it were possible to solder in an oxygen free atmosphere, perhaps that would solve the problem.
Richard,
Soldering in a kiln with a controlled atmoshere? A frien and i
had this disscussion a couple of days ago and i have and idea
that may or may not work and i have as of this date not tried.
Maybe someone out ther has or is interested in trying this so
here it is: (hope this makes sense) Soldering in a kiln is a
matter of raising the temp in the kiln to a high degree of
temperature, depending on the temperature of the solder being
used. The air in the kiln is being heated and forced out of the
kiln in positive pressure atmosphere and is being replaced by
cooler air that circulates in from the bottom of the kiln as hot
air rises. Now if argon were introduded into the heating chamber
under positive pressure it seems to me that it would replace the
air to a large extent and possibly reduce the oxidation. The
argon could be piped in through a long stainless tube through the
pyrometer access hole. The argon turned on and aloowed to fill
the chamber turn on the heat and keep the pressure on. I’m sure
it would take a pressure guage and some practice. I plan on
trying it some day maybe so. Argon is inert and heavier than
air/no oxy no firescale? anyone?
Personally, I don't think that a kiln would work for soldering to avoid firestain. It's the oxygen in the air which causes firstain when the silver is heated. It reacts with the copper which then oxidises. If it were possible to solder in an oxygen free atmosphere, perhaps that would solve the problem.
This could work for soldering silver. To make mokume-gane the
metals are clamped together and sealed in a bag fabricated of
very thin stainless steel which also contains some pieces of
charcoal. This is placed in a kiln and raised to just below the
melting point of the lowest melting component. The charcoal
reacts with oxygen to form carbon dioxide which effectively
removes oxygen from reacting with the metals. Therefore if carbon
dioxide or nitrogen don’t react with silver at the temperatures
used this might work.
Mike McKim
never heard of that stainless steel bag before…how
thin?..where did you get the sheet?
am getting prepared to make my first billet of mokume in the
kiln and am very concerned about oxidation
thanks
derek morton
DMorton@aol.com
The charcoal reacts with oxygen to form carbon dioxide which effectively removes oxygen from reacting with the metals.
G’day: Pardon me for butting in, but in the sealed box the
atmosphere would be carbon monoxide/dioxide, and the monoxide is
the reducing (oxygen-hungry) agent. But it/they would halt the
progress of incoming atmospheric oxygen anyway. Cheers,
/\
/ / John Burgess,
/ /
/ //\ @John_Burgess2
/ / \ \
/ (___) \
(_________)
derek - consider pumping argon into your kiln. Mike
never heard of that stainless steel bag before...how thin?...where did you get the sheet?
I saw some listed in the MSC Industrial Supply(800-645-7270)
catalog. It’s sold in rolls, .008 inches thick X 12’’ wide X
100ft long, price $80.00 per roll.
I have no conection with MSC, other than as a satisfied
customer.
Dave
Hi. Imake sterling silver cuff bracelets which have to be annealed
before they can be formed into the compound curves of the bracelet
shape. I would really appreciate any info on how to prevent the deep
firestain or how to remove it so that a clear high polish can be
achieved? Thank you all.
Also thank you for all the great info that I have learned from just
lurking through the answers to other peoples questions in the past.
Gailee
Hi Gailee, Before touching your piece of silver with a torch, dip it
or brush coat it with a solution of boric acid (or borax, both seem
to work) and denatured alcohol. Then just touch it with the torch to
set it alight and let it burn out. (Be careful - as with other
alcohol flames, the flame is very hard to see, light greenish, so
make sure it’s out before putting your hand anywhere near it.) This
process deposits a microscopic coating of borax over the silver’s
surface, which protects it from developing firestain. The process is
called “burning off.”
Once it’s burned off, go ahead and flux, solder, anneal, whatever
you need to do. The hard part is remembering to do it each time
BEFORE you heat the piece.
Once you’ve got firescale (the dark gray kind), it’s really pretty
impossible to remove, without just continuing to sand away until
you’re deeper than the scale. But that’s rarely practical, as it
goes pretty deep.
If you’ve got pink fireSTAIN, on the other hand, that’s easy to
remove. Once you’ve pickled the piece, if you have coppery stain
remaining, dunk the piece in a roughly 50/50 mixture of pickle and
household-strength H2O2 (hydrogen peroxid) and soak until you see the
copper stain turn gray or brownish. Then, it can be washed away with
your brass brush or toothbrush when you scrub the piece. Works like
a charm.
Good luck!
Karen Goeller
@Karen_Goeller