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 Replies: 30 / Views: 10,060 |
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Pillar of the Community
United States
1215 Posts |
Hey, was wondering whether it would be good to clean silver coins with baking soda and aluminum.
This method differs from using acid in that rather than corroding away the oxidation layer, it reverses the oxidation chemical reaction, thereby oxidizing the aluminum and reducing silver sulfide back to silver. Thus, it's not cleaning in the traditional sense as it does not leave corrosion signs or acid or look of coin being dipped.
I just have an ugly morgan that would otherwise be au55 in my opinion but according to PCGS, ugly eye appeal lowers 2 points, thus giving it a grade of AU53 only. I want it to go back to original toning then let it retone slowly.
Has anyone done this before? I might want to first test with some culls/ junk silver Edited by 0xDA71D
10/18/2014 11:54 pm
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Pillar of the Community
Canada
2517 Posts |
I posted a while back about this: https://goccf.com/t/184658. I don't know how well it works though, since I don't have any blackened silver to try it on. |
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Bedrock of the Community
Australia
21786 Posts |
I have a couple of VERY blackened sulphided patinated silver coins of bullion value only.
I might give it a try!
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Pillar of the Community
United States
6370 Posts |
I used this on a black EF+ Barber dime, and it brought out the luster and made it look more AU than EF. It still resides in my type set as of now. |
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Pillar of the Community
 United States
1215 Posts |
I may try it then! Thanks. Any harm it does to the coin?
The reason that I want to clean my ugly morgan is that it really lacks eye appeal and the spotty toning goes as far as to obscure the main devices on the coin and make it look more like a PO01 coin, but with AU details. And I want to bring it to its true AU-55 condition.
It can turn anyone off in hand, not to mention in a photograph.
Edited by 0xDA71D
10/19/2014 12:32 pm
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Pillar of the Community
United States
589 Posts |
Just be careful, I've read that instead of truly reversing the chemical reactions and keeping the metal where it was, it can remove some silver and redeposit it elsewhere on the coin, possibly creating bumps. At least that's what I've read...haven't confirmed or disproved it myself...just something to keep in mind as a possibility.
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Pillar of the Community
United States
1215 Posts |
Anyone have some ugly junk silver to test this on? I personally don't -- All my junk silver is so worn that there is no notion of them being ugly.
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Pillar of the Community
1153 Posts |
I used this method on a junk 64 quarter, it does work, but you will have an obviously cleaned coin IMO. Don't use it on anything valuable.
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Bedrock of the Community
United States
17884 Posts |
When the tarnish forms it rearranges the structure of the silver atoms/molecules/ crystal structure. When the silver sulfide is reduced the silver does NOT go back where it came from. So you can still end up with a lackluster or cleaned appearing coin. And some of the silver IS still lost into the solution during the cleaning process. The baking soda/aluminum foil cleaning is not a completely safe non-damaging form of cleaning.
Oh and you will still have to be careful to thoroughly rinse the coin afterward. A base like baking soda can corrode the coin if traces are left behind, just like an acid would.
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Pillar of the Community
United States
1215 Posts |
Oh thanks for the info, conder101. Do you think it would be worth it for me to clean my 1921-s Ugly Morgan dollar in AU53 (Could have been AU55) ? |
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Pillar of the Community
United States
1215 Posts |
But wait-- the silver atoms do not go into the solution. Silver sulfide is considered slightly soluble (read: insoluble) in water.
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Pillar of the Community
Canada
2517 Posts |
I think what Conder is saying is that when silver binds with sulphur, the structure of the silver atom changes (ionic bonding -> 2 silver atoms gives electrons to sulphur atom) and you get a salt through ionic bonding. The bonding causes the structure of silver sulphide to be different than silver (which is metallic bonding). When you remove the sulphur atoms, the silver atoms stay in the same place and do not move back to its original place.
It doesn't matter if silver sulphide is insoluble in water. You're using a basic solution, and the silver will react to the base (but slowly since baking soda AKA sodium bicarbonate is a weak base). Some silver will be lost.
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Pillar of the Community
Canada
3692 Posts |
Speaking from experience in polishing metals:
People frequently ask me about baking soda being able to clean silver. I always tell them don't polish things yourself unless you know what grades of grit do. Baking soda is a powder, almost like sand. The smaller the grit the higher the polish, therefore I discourage it for things with a high (mirror) polish, unless that item is a satin or matte finish and even then the direction of the polishing lines count for a lot so you have to know what you're doing and you must have good eyesight. Especially for coins where the dies are high polish, therefore they imprint the same polish onto whatever they strike, so polishing a coin ruins it every time. Now if the coin is old and you're just getting rid of some buildup, fine, just remember that the coin will never be in mint condition ever again.
My 0.02
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Pillar of the Community
United States
937 Posts |
@ 0xDA71D Perhaps you should find a PCGS graded coin with some ugly tarnishing onit, crack it out and apply your baking soda and aluminum to it. Then send it into PCGS to get it regraded. Of course document the process here and let us know how it grades afterwards.  |
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Moderator
 United States
23522 Posts |
Quote:Do you think it would be worth it for me to clean my 1921-s Ugly Morgan dollar in AU53 (Could have been AU55) ? Probably not - that's a $20 coin either way. |
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Bedrock of the Community
United States
19943 Posts |
This old method is a sure way to completely ruin your coin. The only proper way to remove silver toning is with an acid-thiourea dip solution.
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Replies: 30 / Views: 10,060 |
Posted 10/19/2014 12:57 am
