Hello Again,
I understand that depletion gilding sterling silver is helpful in
fighting firescale. What other applications would depletion gilding
prove useful? i.e. in finishing, texturing…
If we chose to use depletion gilding on say, a ring, would it not
make the finish more susceptible to marks/scratches as a layer of
softer fine silver has been created?
Thanks for your input,
Chris
St. Louis, MO
I understand that depletion gilding sterling silver is helpful in fighting firescale.
No, no, no, to fight fire stain one must practice proper fluxing and
flame control. Depletion gilding can attempt to hide fire stain just
like plating can attempt to hide it but with less success as
depletion gilding is much thinner layer than typical plating. And
firescale is the black oxides on the surface that pickle removes not
the reddish purple sub surface color of fire stain
What other applications would depletion gilding prove useful? i.e. in finishing, texturing...
If we chose to use depletion gilding on say, a ring, would it not make the finish more susceptible to marks/scratches as a layer of softer fine silver has been created?
The layer of fine silver left by depletion gilding is incredibly
thin. Metals are not porous to the larger molecules of liquids. So
the acid can only effect the surface of the metal, all it is doing
is leaching out the copper oxide from the outermost surface of the
silver and once it is gone the process quits working. It can not get
at any of the copper oxide beyond the first layer or two of atoms.
It is only useful on items that have minimal handling as it will be
rubbed off very quickly.
James Binnion
James Binnion Metal Arts
I understand that depletion gilding sterling silver is helpful in fighting firescale. What other applications would depletion gilding prove useful? i.e. in finishing, texturing...
Actually, depletion gilding is a poor approach to fire scale. The
reason is that fire scale itself is not really a problem. The problem
lies with it’s close cousin, what’s called fire STAIN. Fire SCALE is
the black surface oxide formed on the metal when heated in the
presence of oxygen. It is not a problem simply because that black
oxide is completely removed by simple pickling. The result is a dead
white color of fine silver. Repeating this heating and pickling
makes the fine silver layer at the surface thicker, as the copper
gets depleted from near to the surface. Brass brush burnishing of
that fine silver surface can help compact it and make it more
durable, but it is, as you suspect, softer than sterling itself, and
that’s not helped by the annealing that takes place with the heating.
Other than simply giving you a matte white surface, or for
reticulation, depletion gilding has few other specialized uses that
require it. A few unusual enamelling situations can use it, but I’m
not aware of other situations where it’s specifically the solution to
a problem or need. Textures are usually mechanically applied, for
example, and though you can depletion gild a textured surface, again
this is only adding that matte white look to whatever you already
achieved.
The real problem with depletion gilding is not, as I said, fire
scale. It lies with what’s under the depletion gilded surface skin.
There, where copper has not been totally depleted, it has
nevertheless combined with oxygen (highly mobile in hot silver or
gold) to form the red oxide of copper, which remains imbedded in the
metal. It’s below the surface, so pickle does nothing. It becomes
the problem if you go to finish and polish the piece instead of
leaving the pristine depletion gilded surface as is. Then, you see
the blotchy look of patches of fire stained metal alternating with
where you’ve managed to buff through it, to the deeper clearer color
of the undamaged silver. And solder joints made to a fire stained or
depletion gilded surface can sometimes, because of the multiple
layers of metal composition and oxide layers, be less strong that
solder joints made to clean unoxidized metal.
Depletion gilding has it’s purposes, for the dead white
characteristic matte surface, or importantly, as the initial process
to prepare metal for reticulation. But if fire scale and fire stain
is your concern, you’d be MUCH better off learning to simply prevent
their formation in the first place. The proper use of Prips flux, or
commercial fluxes intended to prevent fire scale/fire stain (such as
Cupronil), solve the whole problem by not allowing any oxidation,
either at the surface, or down into it. And these preserve most of
the initial finish of the metal too, rather than forcing you to have
a matte dead white surface. Please note that ordinary soldering
fluxes, or the usual boric acid and alcohol dip used by goldsmiths to
protect gold when heated, do not protect silver from fire stain.
What’s needed are fluxes specifically designed as less active, but
high temperature resisting, so they can fully protect the metal
without burning away, as some soldering fluxes tend to do. Check the
archives here on Orchid for prior discussions on Prips flux
preparation and use. It’s cheap to mix up yourself, and once you get
the hang of how to use it, easy enough, and highly effective.
Another easy solution to the problem is to switch from standard
sterling silver to the specialty alloys made to avoid fire stain and
fire scale formation, such as Argentium or others. These simply
pickle clean after heating/soldering, with no concerns for fire
stain.
Hope that helps
Peter Rowe
Chris -
I used depletion gilding if I am going to enamel or keum boo on
sterling silver.
best regards,
Kelley Dragon
I understand that depletion gilding sterling silver is helpful in fighting firescale. What other applications would depletion gilding prove useful? i.e. in finishing, texturing...
I was taught to use depletion guiding if you want to fuse gold foil
(keum boo) to your sterling silver sheet instead of paying for fine
silver. We always brushed the sheet after heating it with a wire
brush to burnish down the fine silver layer.
Christine
www.christinebossler.com
You could try burnishing or tumbling the pieces after depletion -
that will compress and harden the fine silver or gold on the
surface, to some extent. But as with all plating and gilding,
remember that these are not permanent effects - they will wear away
with time, and if the item is also set with heat-sensitive stones or
enamel, you might have a hard time restoring that finish if the
customer requests it in the future.
When using silver, enamel should be applied to a surface of fine
silver. So if you depletion gild sterling, you can enamel on it.
Good afternoon! Does this keep the white colour that it gives?