but I run into something that looks as heavy firestain which is
almost impossible to cover by depletion gilding
Eva, firestain is a virtually unavoidable aspect to reticulation.
Here’s why: We prepare the metal be repeatedly annealing and
pickling, right? What that does is not, as it’s often incorrectly
described, “bring up the fine silver”. The silver is already there,
and hasn’t come up. What happens is that we’ve oxidized the copper
that’s in the surface layers of the silver. then pickling removes the
copper oxide. Copper oxide is also a larger molecule, so it’s not
“comfortable” simply in the original position in the metal. When you
anneal, as with almost anything in the alloy, molecules diffuse, or
move around some. In the case of the copper oxide, it too diffuses
around upon heating, but unlike pure metals in the alloy, if it
happens to reach the surface, then it stays there. All in all, the
result is to deplete the surface layers of copper. Doing this
requires that oxygen is present during the heating, in order to
oxidize the copper at and near the surface, or which may diffuse up
to the surface upon heating. But oxygen is also capable of diffusing
INTO the silver. It doesn’t just wait at the surface. To a degree,
this aids in oxidizing and removing the copper in the surface, which
is what needs to happen to prepare the metal for reticulation. But
there is a depth beyond which the copper is not removed, but where
oxygen has reached, so there remains copper oxide. In preparation of
reticulation metal, the annealing process is repeated a number of
times, so the depth to which this effect reaches, just like the
effect of actually removing copper, is more than what one would get
with just one normal anneal. In effect, then, that layer under the
fine silver is the fire stain layer, and it too is increased in
thickness over a normal anneal. In fact, that layer also plays a part
in helping the surface to not melt during reticulation, allowing the
process to work. But as you’ve found, it is fire stain, not a clean
silver surface. This is simply one unavoidable part of reticulating
sterling silver. Rather than trying to prevent it (you can’t, really)
or remove it (also difficult or impossible without damaging the
reticulated texture), the answer is to increase the fire stained
effect to get full coverage. What you do is fully finish your piece,
and then, the final step is a prolongued somewhat low temperature
anneal with the surfaces very clean, no protectant, etc. Then a
careful pickling and just the lightest subsequent finishing to
restore whatever level of polish you wish. If your surface was
polished well before you did this, then only very light work will be
needed, and the idea is to not cut through the fire stain layer, so
the whole surface is then a uniform fire stain color rather than the
color of clean silver. If it’s not spotty, that difference is not
obvious to the eye. More, traditionally a reticulated surface is
often patinaed with liver of sulphur to enhance the textures. Doing
this on the fire stained surface will further mask any difference in
color.
This solution to fire stain, by the way, is not unique to
reticulation. The famous historical silversmithing firm of George
Jensen (nor sure I spelled that right…) used this process as the
final finish on much of their hollow ware…
You can also repeat the process of multiple annealings and
picklings, as you did before reticulating, which can remove, again,
the copper oxides and copper that is near the surface. If you do
this, you then must be careful not to polish or otherwise work
through that thin layer of fine silver on the surface. Finishing with
a fine brass platers brush to burnish the surface, rather than
actually buffing it, is one good way (just as it’s a good way to help
prepare the initial surface for the process.)
Hope that helps
Peter Rowe