ASK THE EXPERT, Hydrogen Peroxide Pickle, by Bill Seeley
ElaineEC
for the removal of cuprous (red) oxide from copper based alloys.
by Bill Seeley
Disclaimer of Liability
Reactive Metals Studio, Inc. and the author assume no responsibility and
disclaim all liability for injuries and/or damages and/or loss of profit
from the use or attempted use of the processes and formulas described in
the following paper.
As is the case with all corrosive solutions, these formulas should
be handled with care and in good ventilation.
Heat-treating and soldering of copper and copper based alloys can
often coat the metals with a combination of black (cupric) and red
(cuprous) oxide. The black oxide is easily removed in a standard warm
sulfuric acid pickle or Sparex bath. This will leave a red smut, which,
with other undissolved oxides, forms a red oxide scale. This scale
readily oxidizes further, leaving a dark, nonuniform patina. Oxides can
be imbedded in the metal during subsequent forging and drawing, so it
should be removed. Abrasive removal of the oxides can result in loss of
design details and crisp edges on finished work. The following simple
chemical treatment is offered as an alternate method for its removal.
Hydrogen peroxide (H2O2) pickle eliminates the need for abrasives,
and has the added attraction of being relatively inoffensive. The
following procedures and formulas provide for the removal of red scale
from copper, brass, bronze, nickel silver, reticulation silver and some
gold alloys. It will remove the copper coating from silver that has been
accidentally pickled in an iron contaminated acid bath. Curiously, it
will also remove the natural oxide layer found on some aluminums. There
is a great deal of latitude in the formulas and a variety of surface
finishes and textures can be obtained.
It is suggested that you run some tests before applying these
formulas to your work. Find the procedure and formula that best fits your
needs. When working with any acid or strong oxidant the possibility of
damaging your work always exists. These formulas can dissolve a brass
piece and leave the silver solder seams standing.
Some points to remember when using hydrogen peroxide pickles:
1) Adding more acid to the solution will not improve
its action. The acid is just a catalyst or starter.
2) Iron and silver will tend to shorten the life of the bath.
This does not mean you cannot put these metals in
the bath. It just will not last as long.
3) Use only diluted sulfuric acid pickle, Sparex or
vinegar as the catalyst in these solutions.
4) Use 3% hydrogen peroxide available in drug stores, or
mix a 2-3% solution from distilled water and concen-
trated H2O2 (usually 30%), available through a
chemical supply house. More concentrated hydrogen
peroxide pickles (5%) can be mixed when deep, fast
etching is desired. (Warning! Concentrated acid
and strong oxidizing agents are very dangerous.
30% H2O2 is rocket fuel, it is explosive and not to be
toyed with. Do not attempt without proper training
and equipment.)
5) Use these solutions warm(110xF), or about the tempera-
ture of a hot bath. I usually set up a double boiler arrangement. The
hotter the pickle; the faster and coarser the etch
and the shorter its life.
6) Be smart, wear protective clothing and gloves. Do not
work with chemicals alone. Work only in a properly
ventilated area.
The following formulas can be made up as needed, or they can be
premixed and kept for an extended time in the original brown bottle. They
can be reused until saturated (blue) or it stops working. Hydrogen
peroxide decomposes rapidly when exposed to light(That is the reason for
the brown bottle.). The active life of these pickles is limited to about
four exposed hours. You can extend the life of the solution by storing it
in
the brown bottle.
When there is a sulfuric acid component in these solutions it is
already diluted with water to a standard pickle consistency of 5-10%. The
catalysts can be either measured or slowly added until bubbles begin to
appear on a test sample of the metal. This signals that the solution is
active.
SOLUTION #One (mild):
2 parts Hydrogen Peroxide (3%).
1 part water.
2-4% fresh sulfuric acid pickle(5-10%) or Sparex solution.
SOLUTION #Two (strong):
1/2 cup Hydrogen Peroxide (3%).
1 Tablespoon fresh sulfuric acid pickle(5-10%) or Sparex solution.
PROCEDURE:
STEP #1: Prepickle the piece in standard Sparex or sulfuric acid pickle
solution and rinse well. All the black oxides should be removed in this
step.
STEP #2: Place the Hydrogen Peroxide pickle container in a second bowl
of hot water to keep it warm. If possible suspend the piece in the warm
pickle or stir it gently with a feather or plastic rod . After a moment
bubbles should appear on the piece. Agitate or brush with a feather to
clear the bubbles. Remove the piece from the bath every couple of minutes
to check the progress. It may take 5-10 minutes. Rinse well.
STEP #3: Use a stiff tooth brush or brass brush to remove residue and
rinse.
STEP #4: Pickle again in standard Sparex or sulfuric acid solution (5
10%) to remove any remaining smut.
STEP #5: Repeat steps #2, #3 and #4 if necessary.
SOLUTION #Three: (For the weak at heart!)
3 parts Hydrogen Peroxide (3%).
1 part white vinegar (5%).
PROCEDURE:
Follow the steps #1-3 listed for solutions #One & #Two. When the metal
emerges from the pickle, it will be coated with a thick brownish green
smut. Really ugly! This will flash off when dipped in undiluted white
vinegar.
Notes:
These solutions can also be applied to warm metal with a brush and worked
into hard to get corners and intricate designs.
Long term exposure to these pickles can cause the copper to be
dissolved out of an alloy's surface. Brass, for instance, can be pickled
until it turns bright yellow. Even the mildest of the vinegar solutions
can deeply etch if left unattended. A deep etch will often reveal the
underlying crystal structure of the metal. Care should be taken and the
process watched closely.
This paper my be copied and distributed freely as long as no payment
is accepted.
Hydrogen Peroxide pickle does not remove firescale from sterling
silver. That oxide is black, not pink! Sorry!
Bill Seeley developed this formula while studying for his jewelry MFA
in the Department of Design at the University of Kansas. The formulas are
reverse engineered from a more toxic commercial application of hydrogen
peroxide.
Bill Seeley MFA / Member-SNAG
Reactive Metals Studio, Inc. / Corp.President
PO box 890 Clarkdale, AZ 86324 / Interest-exotic metals
reac...@sedona.net
Tara Kemp
hydrogen peroxide solutions that will remove silver firescale. Does
anyone know of such formulas or is this just a pipe dream? Any other
ideas? I use warm sparex in a fairly strong solution but it doesn't seem
to budge the firescale.
Tara Kemp
Tara Kemp
Tara Kemp
Tara Kemp
Tara Kemp
Tara Kemp
little tussle with my computer. It kept telling me it could not send my
letter, so I kept trying not knowing it was sending it out on each
failed attempt. I'm new to this newsgroup and very glad to have found
it. Guess I made a BIG first impression!!!!!!!!!!
Tara Kemp
Tara Kemp
Tara Kemp
Tara Kemp
Tara Kemp
Tara Kemp
Tara Kemp
Tara Kemp
Tara Kemp
Tara Kemp
Tara Kemp
Tara Kemp
Bill Seeley
***Tara, There are only two ways I know of to attack fire scale. One is
with a nitric acid solution. This of course has some dangers. Not only
to the operator but to the piece you are trying to clean up. It is
discussed in some of the older jewelry texts. The other is, of course, a
product I sell. It is called MultiEtch and is made by some friends of
mine and in our current catalog. It was developed for cleaning titanium
and is a strong oxidizer(like H2O2) and will remove light, I say light,
fire scale. Again long durations in the solution can cause damage to the
work. Be very carefull.
The other thing is to protect your metal with lots of flux and keep your
temperatures down and the duration short. Choose lower temperature
solders. There is no reason not to use Easy and Medium solders. Tests I
ran in college showed little significant difference in the strength of the
joint. Bill
--
Bill Seeley, Reactive Metals Studio, Inc. PO Box 890 Clarkdale, AZ 86324, 520/634-3434, FAX 520/634-6734, 800/876-3434 We are titanium & niobium suppliers to the world of art & beauty. Small & personal, we know our customers and our products. Fouteen years in the business. Free catalog!
PeterWRowe
>
>I enjoyed the informative 'pickle' article. I have heard tell of
>hydrogen peroxide solutions that will remove silver firescale. Does
>anyone know of such formulas or is this just a pipe dream? Any other
>ideas? I use warm sparex in a fairly strong solution but it doesn't seem
>to budge the firescale.
>
>
Although there are formulas published for "bright dip" solutions for fire
scale removal, I've never yet had really satisfactory and consistent
results with them. And believe me, I've tried...
You can try reverse electro plating, or electrostripping, which does work
to a degree, but tends to work best on high spots, which are easy to
polish, and leave the low and recessed areas, where you really need the
help, alone.
The more traditional use of H2O2 in the jewelry industry is the process of
peroxide/cyanide bombing, which is the mixing of sodium or potasium
cyanide solutions (hot) with concentrated peroxide. The result will
actively react, and in some cases, almost explode. But at the same time,
far beyond merely cleaning up fire scale, it can literally polish 14K
yellow golds,even inside the most intricate details, and if repeated a
number of times, will dissolve enough of the surface of a silver casting
away to have removed the fire scale (along with a certain depth of the
silver surface). It tends to leave, after this, a somewhat coarser pebbly
surface, which may need considerable additional finishing (though steel
shot tumbling/burnishing works well). Fire scale on fabricated silver
items can be removed in fewer steps, with less damage to the surface
finish.
But as Bills article suggested when he referred to his procedures as
being derived from "more toxic" industrial procedures, this is a very
nasty mix of chemicals. You're now using 30% H2O2, which can litterally
start a fire, or burn your skin, just like concentrated sulfuric acid.
And the cyanide solutions are extremely poisonous. And then you're
violently reacting the two together ( meant it when I used the word
explode).... Clearly not for amateurs and home workshops, even if it
really does do wonders sometimes.
A far, far, better solution to fire scale is to avoid it's formation. In
casting, this can be impossible with standard sterling silver. But there
are fire scale free alloys which can be used, though they tend to be more
brittle, especially when hot, and larger items can crack in casting. In
fabrication, though, you can quite easily limit or eliminate fire scale
altogether by the use of Pripps Flux, sprayed onto the entire silver
piece, prior to soldering or annealing. If you are not familier with this
safe, home mixed and completely effective flux, let me know, and I'll
(yet again ;-) ) . post the formula and procedure...
Hope this helps.
Peter Rowe
Cathryn MacFarlane & Paul Scott
RE: Mention of posting of formula for Pripps Flux...oh,please,please
post it.
Thanks
Cathryn
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says...