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Old 02-12-2018, 02:15 PM
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ArthurEvans ArthurEvans is offline
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Default Thiosulfate works on copper, not silver...

In the thread titled "Cleaning copper - If you want to"
http://metaldetectingforum.com/showthread.php?t=256868
I showed how sodium thiosulfate, a common chemical used in B&W photography, spa treatments, and medicine, reversed the black tarnish on pennies, though not the green corrosion...
Before-
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After only minutes (though a little HCl was applied in a second step to take off some of the green corrosion, which is probably CuCO3) -
Name:  penny after.jpg
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I tried it on a silver bowl (found in the attic, not under the soil), and discovered that this method doesn't work on silver.
Before-
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After an overnight bath in sodium thiosulfate -
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It *might* have moved the thicker tarnish around a little, but it seems overall to have caused much more tarnish on the surface. Some reactions of thiosulfate do release sulfur though ... so it seems an effective way of creating patina on silver, if you ever want to do that... In case someone tells you that your silver is worth less because you cleaned it, you might want to try this!

I wasn't happy with leaving the bowl this way, so I tried the good old bath of baking soda and aluminum foil... It was still hot when I put it in. It took all of five seconds to do this...
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There's still some of the thicker tarnish. I don't understand all this yet, but right now my theory is that a very thin layer of tarnish can be reversed without losing any silver, but that if it builds up too thick, then it can't be chemically reversed without the corroded silver coming off. When I buffed this on a cloth afterwards, the cloth turned black.

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Old 02-12-2018, 11:10 PM
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cellrdwellr cellrdwellr is offline
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Really cool read, Thanks for sharing!

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