01 September, 2014

Cleaning silverware with SCIENCE!

Maryanne and I picked up a really nice antique silverplate service Saturday at a little antique shop outside of Pittsfield with the intent of putting it to use as our everyday flatware. It was moderately tarnished, and today I set to work with the silver polish to try and get it back to lustrous beauty.

And after about an hour of work to get half a dozen pieces done, I decided there had to be an easier way. Dr. Google, as usual, had some great suggestions. I decided to use the one that presented the least amount of work.

Set a large pan on the stove and line it with aluminum foil and lay out some silverware on the foil. Every piece of flatware must be touching the aluminum somewhere, even if it's only a small point of contact. Pour water into the pan to cover the silverware by a couple of inches and turn the fire on under the pan. Bring the water to a full boil.

Shut the heat off under the pan and sprinkle the water liberally with baking soda. The water will appear to foam as the baking soda works, and there may be a "rotten egg" smell. That's hydrogen sulfide, a byproduct of the chemical reaction cleaning your silver.

Hydrogen sulfide is poisonous, but you'd have to seal yourself inside a plastic bag along with the reaction to get a dose big enough to do you any harm.

The foaming will stop after a few minutes. Leave the silverware in the solution for a little while longer to allow the reaction to work as completely as possible.

Remove the silverware to a dishpan filled with warm, soapy water and clean it thoroughly. The tarnish should be mostly gone, and the silver will have a lovely matte finish. If you want a more shiny look, finish off the cleaning job by quickly buffing it up with a bit of silver polish.

<<- Before

After ->>

So how does this all work?

Silver combines with sulfur compounds in the air to form silver sulfide, which is black, and appears on the surface of the silver as tarnish. Removing the silver sulfide coating from the surface makes the silver shiny again..

You can remove the silver sulfide two ways: scrub it off the surface (i.e. use silver polish) or reverse the chemical reaction (i.e. turn the silver sulfide back into silver.) The method I used uses a chemical reaction, sped up by heating the water, to turn the silver sulfide back into silver.

Aluminum has a lower ionization energy than silver - it takes more energy to remove electrons from a silver atom than it does from an aluminum atom. During the cleaning process, the aluminum foil is oxidized (loses electrons) and the silver is reduced (gains electrons.) The silver turns bright and the aluminum foil darkens as the tarnish is "transferred" from the silver to the aluminum.  Because this is an electrochemical reaction, the silver and the aluminum must be touching.

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