Silver will tarnish - 'tis the nature of the beast! Even Argentium
and the other tarnish resistant silver alloys will tarnish, though it
will take longer than regular sterling silver.
Ear wires and posts should never be sprayed with anything, in case
of setting up reactions in the delicate piercings in your clients’
ears (or anywhere else…)
I find by far the best way of going about this is to educate your
clients. If asked about silver tarnish I’m always honest and tell my
clients that it will always tarnish - the speed at which it does so
is often dependant on the environment (in towns with lots of
sulphurous car exhausts it will go much quicker than in the country
where there isn’t - generally - so much sulphur) It also depends on
the individual’s body than others.
Teach your clients how to care for their silver - tell them to keep
individual pieces in little plastic zip-lock bags when not being
used: perhaps with a small square of anti-tarnish paper. A wipe over
with a silver polishing cloth followed by a good rinse in clean warm
water is a good way of keeping tarnish at bay. You could sell (or
give) them small polishing cloths with their new jewellery.
There is a whole lot of stuff on the web in general and Ganoksin in
particular about cleaning silver.
I have found that most people appreciate it if you are completely
honest with them, and even after learning that silver will eventually
tarnish unless they do a bit of maintenance on their jewellery, they
usually go on to buy my silver pieces. For which I am truly grateful!