There is yet another way – repeated pickling to "depletion gild"
the silver. Pickle well in new, clean pickle. Lightly brush the
piece, then mildly heat it. Pickle again. Repeat the brushing and
pickling. Repeat again. After several (3 or 4 or 5) repetitions,
the silver will have a frosty appearance. All the copper will have
been leached from the surface. The frosty appearance, I am told, is
because after systematically removing all the copper from the last
few microns of the surface, it is left microscopically porous.
I have admired this treatment, and was given this explanation. In
the last couple of years, there have been a number of pieces that
used the depletion technique which appeared in gallery shows at the
National Ornamental Metal Museum, and even in the gift shop. It does
seem to wear through easily, leaving burnished highlights. I have
not deliberately tried to use this technique – yet – but several
pieces began to have this appearance after several picklings. The
surface is much finer, and much more matt, in my opinion, than those
which sand or bead blast, steel wool, brush, scotch-brite, or
combinations or these is used.