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Firestain on silver


#1

Kenneth.

I am
considering using fine silver for some of the constructed work we
do. I am not sure if it will be strong enough, I’ll have to
experiment and see. Eventually I think there will be a deoxidized
sterling sheet and wire available, but I am not aware of any
source for that yet.<<

Using fine silver would obviously increase production costs. The
cause of firestain on silver is the copper which is used to make
an alloy and to make the silver harder/ stronger. If the copper
was replaced with some other metal then I would think that the
problem would be solved. There is a propreitory coating made by
JM whic can be brushed over the surface of the silver to protect
the silver while it is being soldered, but this tends to run into
pools and leave patches of oxide which are just as difficult to
remove.

Richard


#2

Richard wrote:

Using fine silver would obviously increase production costs. The
cause of firestain on silver is the copper which is used to make
an alloy and to make the silver harder/ stronger. If the copper
was replaced with some other metal then I would think that the
problem would be solved. There is a propreitory coating made by
JM whic can be brushed over the surface of the silver to protect
the silver while it is being soldered, but this tends to run
into pools and leave patches of oxide which are just as
difficult to remove.

Richard

Richard:

I realize fine silver costs more than sterling. However, fine
silver could be processed with mass finishing equipment and
thereby offset labor costs. I hate buffing production work and am
suspicious of anyone who doesn’t (grin). I am curious to try the
deplating method you have described. What is involved? What
chemicals are used. What type of surface is left? I have no
plating experience, but would be willing to try anything that is
effective and manageable for production work.

As I understand it the deoxidized sterling silver casting grain
is not quite as strong as traditional sterling but close. At this
time I am not aware of any company that processes any deoxidized
sterling into sheet and wire. I do not know why there isn’t, but
am anxiously awaiting. I am sure it will be more expensive than
traditional sterling just as the casting grain is, but so is
mechanically removing firestain.

Thanks for you input and let us know about the deplating process
you wrote about.

Kenneth Gastineau
@Kenneth_Gastineau1


#3

Hi Kenneth,

The problem with deoxidised silver is that obviously they have
been formed in an inert atmosphere, probably they were heated
using argon as a shield. But once they are heated again the
firestain returns. I have tried mechanically removing firestain
with abrasives, but this tends to remove detail as well

This is just a quick resume of the electroplating process for
anyone who is not familiar with it. Electroplating,
electrochemical process for depositing a thin layer of metal on,
usually, a metallic base. In the process of electroplating, the
object to be coated is placed in a solution, called a bath, of a
salt of the coating metal, and is connected to the negative
terminal of an external source of electricity. Another conductor,
often composed of the coating metal, is connected to the positive
terminal of the electric source. A steady direct current of low
voltage, usually from 1 to 6 V, is required for the process. When
the current is passed through the solution, atoms of the plating
metal deposit out of the solution onto the cathode, the negative
electrode. These atoms are replaced in the bath by atoms from the
anode (positive electrode), if it is composed of the same metal,
as with copper and silver. Otherwise they are replaced by
periodic additions of the salt to the bath, as with gold and
chromium. In either case an equilibrium between the metal coming
out of solution and the metal entering is maintained until the
object is plated. Nonconducting materials may be plated by first
being covered with a conducting material such as graphite. Wax or
plastic patterns for electrotype and recording-disk matrices are
coated in this manner. To ensure a strong and close bond between
the object to be plated and the plating material, the object must
be cleaned thoroughly by dipping it into an acid or caustic
solution, or by making it the anode in a cleaning bath for an
instant. To eliminate irregularity in the depth of the plate, and
to ensure that the grain at the surface of the plate is of good
quality and conducive to polishing, the current density (amperes
per square metre of cathode surface) and temperature must be
carefully controlled. Colloids or special compounds are often
added to the bath to improve the surface uniformity of the
plate.

To use the electroplating system for deplating swap over the
terminals so that the work from which you want the firestain
removed is attached to the positive terminal then the silver
object becomes the positive electrode. The current will pass from
the silver object onto another metal object attached to the
negative terminal which will get a deposit of silver. The layer
of firestain on silver is very thin so it should not be
necessary to do the reverse plating process for more that a few
minutes. Trial and error required!! Obviously I don’t accept any
responsibility for any errors

I’d like to hear other folks thoughts on this process, and would
be interested to hear from anyone who has tried it.

Richard

Richard Whitehouse,
Silversmith,
Ardleigh Workshop,
Ardleigh,
Colchester,
UK