Cool Science: Restore Silver with Electrochemistry

How to restore old silver with aluminum foil or a battery by electrochemistry.

Old silver is often tarnished by a thin layer of silver sulfide that appears as a brown color. The silver sulfide can be electrochemically converted back into pure silver if a negative charge is applied.

To do this, first make a solution of equal parts baking soda and table salt (NaCl) and adding enough hot water until they dissolve. Then simply place a silver object in the solution and contact it with a large piece of aluminum foil. In a short time the silver will be restored.

A very cool way to do the same thing is to use a battery. Connect the negative end of the battery to the silver and the positive end to a large electrode, like a copper plate, and dip them both in the solution.

This process occurs due to electrochemical reduction of the silver sulfide to silver.

Special notes:

THIS ONLY WORKS WITH ELEMENTAL SILVER! This restoration method does not work with silvery things like stainless steel or chrome. So make sure the item you want to experiment on really is silver before trying this.


A low voltage battery is best for this experiment, around 3 volts. Higher voltages do not improve the process and may actually damage the item you're trying to restore. If you don't want to mess up, then just use aluminum foil and skip the battery entirely.

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[nuclear12321]

Copper doesn't give electrons easily? What about the Valence electron in its outer shell. ?

Johnishable i think you can, pennies are about 98% copper. It should work

[NurdRage]

@nuclear12321 if you think i'm wrong then try it yourself. put the tarnished silver with the copper and you'll see it won't be restored.

[E5Elias]

Salt is corrosive to silver and there is no need to include it in the solution.

Baking soda and aluminum with no salt works quite effectively

[NurdRage]

@E5Elias Go for it. Personally i didn't have as good results without using the salt. But if you can do it then go for it.

[theplaceboeffect]

This is totally awesome! I'm so glad I found your videos.

I made a good decision when I decided to major in Chemistry. :)

You can bet that I'll be suggesting this experiment (along with the glow sticks!) to my professor.

THANK YOU!

[NurdRage]

@theplaceboeffect thanks!

[Jaxterpeace]

Your voice reminds me of some horror movie i saw.

[ThePhoenixAffinity]

@nuclear12321 since the 80s pennies are zinc coated with copper, im prety sure

[ferencproject]

Totally awesome.... 

[MajorBluntz]

I WAS BLINDED BY SCIENCE!

[mrfphats]

if it wasnt for stumble i may have never seen this

[badshabz1]

I dont understand how the aluminum is oxidised and the other metal is reduced (goes silver) is it because there is large differance is electro-negativitey and is acts like a battery is the nacl and baking powder solution

[serke]

@nuclear12321 Pennies are only 95% copper if minted before '82, after that it's 97.5% zinc with a copper coat. So if you tried it, try again with old pennies. :)

[GodsUnwanted88]

Does this work with .925 silver to? Or only the silver that u got. Cause i tryed some jewelry, and i couldnt get it working...

[Mrkirill578]

What would happened if I force the electrons to flow to the silver by switching the polarity?

[silverleaf81]

@Jaxterpeace I wanna play a game.

[TheCynicalAristocrat]

Alas, something I can actually do at home..