posted on Jan, 4 2013 @ 11:01 AM
Originally posted by Valhall
Well, I referred to it as "patina" but it is mainly called "tarnish" for silver. And that reaction is oxygen dependent (it's silver oxide).
The theory of the temporal shift of the item and therefore it not being exposed to oxygen plus time is interesting.
No, silver patina isn't from oxygen. Silver is one of the few metals that don't react with oxygen readily. (The others are gold, platinum, and
palladium, which is why they're the most precious metals.) Silver tarnish is actually silver sulfide. Silver metal reacts with sulfur-containing
compounds, especially hydrogen sulfide, to form the tarnish. For silverware, the main sources of the sulfur are from foods (especially eggs), but
contact with wool, latex gloves, some paints, fossil fuels, human hands, or acidic atmosphere (sulfuric acid from "acid" rain) can also cause
A salad spoon/spork isn't typically going to come in contact with foods that are high in sulfur. If such a utensil is washed and rinsed well and
wrapped in a cotton or linen cloth and stored, with very little contact from human hands or rubber gloves after washing/rinsing, it will stay
virtually free of tarnish for decades.
(I'm a chemist and I discuss this with my students when we cover oxidation/reduction reactions in class.)
edit on 1/4/2013 by CarolynC because: