G’day - here comes a bit more pedantry: Electrocleaning of
sterling or fine silver is based on the fact that most of the
tarnish is black silver sulphide, which is caused by sulphurin
the atmosphere, or from people’s skins - not much, but it builds
up over time. Removal of the sulphide film can be accomplished
by abrasion (including domestic metal polishes), or by chemical
means. Electrolytic cleaning by immersing the silver into an
alkaline bath with a piece of aluminium in the bottom is one
simple way, though not always effective. Electrolytic cleaning
with an external electrical current works better.
Use a vessel big enough to hold your work, dissolve some
washing soda crystals (sodium carbonate,) - the amount isn’t
important - in hot water in the vessel. (Caustic soda -sold as
Drano in America) is not necessary and only makes the job a bit
hazardous). Connect a wire to a piece of stainless steel; even
an old SS spoon will do, and the other end to the POSITIVE pole
of a car or even a motorbike battery - or a car battery-charger.
Connect another wire to your work to be cleaned, and the other
to the NEGATIVE pole of the battery. The work and the SS
electrode will fizz like mad.
This is where the pedantry begins: The story is that a molecule
of hydrogen gas, consists of two atoms of hydrogen, H2 (the 2
should be in subscript but this don’t work in email!) Now
hydrogen is very reactive and likes nothing better than to join
up with many things, but it needs energy to initiate the
reaction (a little heat for instance).
But monatomic hydrogen H is far more reactive, and when an
electric current is passed through water containing an alkaline
electrolyte like sodium carbonate the energy is used to break
down water into O at the positive pole, and H at the negative,
but they quickly reform to O2 and H2 which dissipate into the
air. However, at the instant of release, the monatomic or
nascent hydrogen, being highly reactive, grabs at the sulphur
film on the work and converts it to hydrogen sulphide (H2S),
which is a gas; the one which makes bad eggs smell bad, though
in this case, there is scarcely enough to notice. Thus the film
disappears.
Oh, by the way, don’t confuse tarnish with the dreaded
fire-stain; they are quite different. And ain’t science
wonderful? Cheers,
/\
/ / John Burgess,
/ /
/ //\ @John_Burgess2
/ / \ \
/ (___)
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