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Depletion gilding


#1
I've heard of it and I've read Charles's paper on it. 

Whew. Thanks, Marilyn. Threads take a long time to develop here.
So what do you think about that original query? How did the
ancient Egyptian gold look the way it does, and can that chap get
that colour with depletion gilding?

Brian


#2
 For those that are not familiar with it, it works like this.
Heat the finished silver and quench hot.  

What is the piece quenched in, oil, water or pickle? I’m sorry
to show my ignorance so blatantly, I’m still new and easily
confused.

Penny


#3

Heat to anneal temperature and quench in hot pickle. Repeat
several times with a burnish or planish after every 2 or 3 times.
You need to burnish the (by now) rather porous surface.

Brian Adam ph/fx +64 9 817 6816 NEW ZEALAND
http://crash.ihug.co.nz/~adam/


#4
What is the piece quenched in, oil, water or pickle? I'm sorry
to show my ignorance so blatantly, I'm still new and easily
confused.

Penny, the piece is quenched in pickel. Slide it in with copper
tongs and use the lid to the crockpot (I hope that’s what you use
for the pickle) as a shield. Rinse, reheat, and pickle until the
piece is dead white.

Marilyn


#5

Brian, sometimes a thread doesn’t ever get started. I don’t know
if it’s because everyone is busy, or if no one has an answer. I
don’t work much with gold so my answer may be wrong but yes, I
think depletion gilding can give the appearance of 24k gold but I
don’t think that it can give the appearance of a red gold because
I understand that it gets its color from the extra copper in its
alloy. The depletion process removes the copper from the surface
and so would take it back to a 24k look. I think that Metalsmith
or Ornament had a big article on the different materials used to
deplete gold by early peoples. Some of them took days or weeks to
be effective. It’s an old process.

Marilyn Smith


#6

What is the piece quenched in, oil, water or pickle? I’m sorry
to show my ignorance so blatantly, I’m still new and easily
confused.

The quenching is done in pickle which leaches out the surface
oxides of the alloying copper leaving a fine silver layer after
several repeats. It is best done with a high copper content alloy
such as 800 silver- reticulation alloys are available from
several refineries includinh Hoover & Strong. Reticulation uses
the same process- the underlying metal flows befor the higher
melting depleted skin.

Rick
Richard D. Hamilton

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

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


#7

I have read the several post on the subject of depletion gilding and
I a m confused. I must admit that I do not have any proof of the
following only m y observations. The only time I ever got the
frosted silver (white finish) was when I pu t castings that were
black after quenching into the pickle pot. My castings come out as
clean silver when I quench after using my firescale free casting
technique. These clean silver castings do not turn frosted if I
leave them in the pickle pot, which I normally do not have to do.
When I used to get black castings I would pickle them, polish them
and soldering on the findings. I have never had a polished piece of
sterling ge t the same frosted finish that a black casting does when
placed in the pickle pot. I believe the frosted finish the silver
gets in the pickle pot is cause d by the removal of the copper in
cupric oxide, the black coating (copper combined with oxygen) and not
the removal of pure copper. If the removal of pure copper was what
caused the frosted finish, polished silver would come out of the
pickle pot with a frosted finish. I believe Wayne got it right when
he said in his post that gilding is obtained by heating the silver to
cherry red in an oxidizing atmosphere whic h produces an oxide rich
(copper oxide) material on the surface. Using a fire coat
preventative flux when soldering prevents the oxides from forming.
There is no copper oxide to be removed therefore no frosted finish in
the pickle pot. Depletion gilding does not remove fire scale, it only
covers it up as lon g as the layer of fine silver is not removed in
polishing.

My 2 cents on the subject

Lee


#8

Hi Lee,

Depletion gilding does not remove fire scale, it only covers it up
as long as the layer of fine silver is not removed in polishing. 

That’s exactly right. Heating the metal causes the formation of two
copper oxides: cupric oxide and cuprous oxide. I can never remember
which is which but one of them forms the discoloration or black stuff
on the surface of the silver (or gold) and is removed by the pickle.
The other lurks underneath the depletion gilded (fine silver or fine
gold) surface as fire scale (and can only be removed by abrasion or
stripping if you want to get rid of it).

If the metal has been fluxed and not overheated, the surface oxide
is removed by the pickle leaving the original alloy (sterling silver
or 14K gold, for instance). If the metal was not fluxed and was
sufficiently heated (usually more than once), you can get a lovely,
even coat of pure metal covering the fire scale. But, if the metal
was fluxed and overheated or heated unevenly, you’ll end up with
patches of firescale marring the surface of the original alloy and
possibly gilded patches as well.

Rachelle Thieves developed a wonderful technique to heat-patinate
sterling silver by taking advantage of this process. Briefly
described, it involves depletion gilding the sterling, then abrading
away the fine silver surface in selected areas only in order to get
back down to the sterling. Next step is to heat the metal one last
time so that the abraded areas turn black but DO NOT put the metal in
pickle. If done right, the result is a deep black pattern on a
bright white background (although the “background” is actually the
foreground). There are some tricks to this process which I don’t
remember offhand but, if anyone’s interested, I’ll go dig out my
workshop notes and pass them on.

Beth


#9

Lee, Your observations concerning depletion gilding are correct. If
a flux is used, no oxidation takes place. If no oxidatio= n takes
place there is no oxide for the acid (pickle) to remove. Heting the
silver in oxygen produces the maximum oxide possible…or gold for
that matter.

Wayne


#10

So are you saying if I want to depletion guild gold or silver, I
should heat the item with the torch using more oxygen than gas,
don’t flux, and try to achieve that icky dark surface? Then I should
pickle and brass brush and repeat? I think I was always trying to
depletion guild using flux. Annette


#11

Annette, You are correct. If you are attempting to deplete the
surface oxides, you must first allow them to form! The prupose of
the flux is to prevent them from forming, so don’t use any flux,
just heat the piece slowly to medium red in air with a b lue flame.
Don’t approach the melting point of the piece, orange color may be
too hot! Someone was complaining that the y got poorly reticulated
surfaces rather then smooth surfaces when repeatedly heating and
pickling…that’s because he we re melting the inner core of metal!
Strong red color is fine, work in subdued light…it’s easier than
it sounds. Wayne


#12

Hi Annette,

  So are you saying if I want to depletion guild gold or silver, I
... don't flux, and try to achieve that icky dark surface? 

Exactly. Fluxing inhibits oxidation and you want the surface to
oxidize so that the metal is depleted of copper at the surface.

Beth


#14

6 posts were merged into an existing topic: Depletion gilding question


#15

An old thread - bumped to top, as it relates to the other thread on depletion gilding.