Many gun “blueing” solutions are Selenium based and even though they
are made for use on steel, often work (with different colors that
you would get on steel) for other metals. The “blue” material will
give a deep, iridescent, purple on bronze if brushed with a brass
brush while wet. You can get brown, black, blue and other colors at
your local, well stocked gun shop and some hardware stores.
Bu(i)rchwood Casey is a primary producer of these materials, so one
may be able to get silver specific mixes directly from them.
However, they usually sell direct in 5 Gallon quantities or more and
the stuff runs in the $40.00+ per gallon range but some shops may be
selling smaller, broken down quantities, just don’t know about the
silver (if available) mixes. With any patina, what you do with the
wet piece (ie the brass bristle brush on the bronze mentioned above)
can make HUGE differences, so one might experiment with different
application techniques, or better yet, a number of interested folks
on this list divvy up different materials/techniques and all report
back to the list with results. Sharing often get more info back
that given… I would participate, but I don’t work with
silver, just bronze sculpture, but I would like to do this with a
group of interested bronze casters/patinaters if I could find a
willing group to do it.