Toning is corrosion!

Discussion in 'Coin Chat' started by TypeCoin971793, Jul 8, 2018.

  1. So I got some powdered sulfur to experiment with some junk silver coins. One of these experiments consisted on baking a coin in this sulfur just to see what would happen. Well, what resulted was a black, crusty mess with few defining characteristics. Thinking that this black crusty stuff was just some caked-on silver, I hammered the coin until the crusty stuff came off so it could be a discernable silver coin again. What I saw shocked me.

    Here was the coin before my experiments:

    FAF9A05C-5CD9-4BE0-832C-EA23E97CF2F2.jpeg 54888E02-934E-4D1C-8540-D6EE05ADC79D.jpeg

    Here is the result. The above coin is on the right. The left coin was another, similar experiment, just not as severe of a result.

    BD644E99-6256-4410-916A-13CB0A5E439E.jpeg C795FE34-FB0C-4752-8DF3-48CB859EBA6F.jpeg

    The coin weighed nearly 4 grams less than it did before! I then started looking at the crust fragments to see what was there to see. On this piece, there are two clear layers. The outermost layer is most likely caked-on sulfur, but the inner one is most likely the coin itself! The inner layer measures about half a millimeter thick, which would explain the drastic weight loss. I found it surprising that the sulfur was able to seep so deep into the coin and react with the silver.


    So remember, when you are buying a toned coin, you are just buying a coin with a thin layer of crusty corrosion. :)
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  3. V. Kurt Bellman

    V. Kurt Bellman Yes, I'm blunt! Get over your "feeeeelings".

    Winnah, winnah, chicken dinnah.
  4. TheFinn

    TheFinn Well-Known Member

    Sulfur does not tarnish coins... sulfide does. You just created silver sulfide which is... black. You were able to get the reaction to go to completion. Good that you used a fairly inexpensive and not-too-rare coin. Eventually all "toning", aka tarnish (which is as you pointed out corrosion) turns to black, and is irreversible.
    Omegaraptor and Stevearino like this.
  5. I know. I am well aware of the chemistry of it. I was surprised the reaction penetrated so deep into the coin’s surface.
  6. TheFinn

    TheFinn Well-Known Member

    It is amazing it penetrated so deeply. What was the amount of time and the temperature that this was done?
  7. -jeffB

    -jeffB Greshams LEO Supporter

    Technically, you've got it backwards. Sulfur certainly does tarnish coins, by combining with the coin's silver or copper to produce sulfides, which are toning/tarnish/corrosion.
  8. green18

    green18 Sweet on Commemorative Coins Supporter

    Tarnish 'eats' to the degree of such, it's connected to the accelerator.
  9. 20 minutes at 350°F
  10. TheFinn

    TheFinn Well-Known Member

    Wow. That is amazingly fast to go so deep. Was this in the kitchen oven? As Emeril would say, "BAM!!!"
    Stevearino likes this.
  11. Yup. Do not recommend using it with coins
  12. TheFinn

    TheFinn Well-Known Member

    Or food now.
    TypeCoin971793 likes this.
  13. Kentucky

    Kentucky Supporter! Supporter

    Try just mixing a little sulfur powder with some soap, rub it on the coin and let it sit a couple of days.
    TypeCoin971793 likes this.
  14. I might try that.

    My main goal of the experiments was to see if I could apply a realistic circulation patina on a coin. This is one of my later results. It was originally a very light pale gray.

    Last edited: Jul 8, 2018
  15. V. Kurt Bellman

    V. Kurt Bellman Yes, I'm blunt! Get over your "feeeeelings".

    It's a gas!
    Kentucky likes this.
  16. Clawcoins

    Clawcoins Well-Known Member

    Email some of the chinese places/vendors, they'll probably give you more tips than you can shake a stick at.

    LOL .. I"m still learning the restoration process with continual improvements.
    though I've actually toned some coins I dried at too high a heat. Oops. nothing high grade and only face value but still interesting learning.
    Stevearino likes this.
  17. It is!

    I’d equate that to negotiating with terrorists. No thanks...
  18. GDJMSP

    GDJMSP Numismatist Moderator

    You know what the interesting part is ? What you did with your experiments in a short period of time with heat - that's what coin albums do to coins over a longer period of time ;)

    So does storing your coins in any proximity to paper or cardboard ! You know, things like original mint packaging, 2x2s, maybe keeping documents and important papers in the same safe where you store your coins. Stuff like that.
    Stevearino and TypeCoin971793 like this.
  19. V. Kurt Bellman

    V. Kurt Bellman Yes, I'm blunt! Get over your "feeeeelings".

    On really old photographs, the image is made of itty bitty crystals of silver, and the mounting boards are largely NOT sulfur free or acid free paper. Guess what.
    Stevearino likes this.
  20. halfcent1793

    halfcent1793 Active Member

    "Experts" used to sell a 10% sulfur ointment in petroleum jelly to recolor copper coins. It converts metalic copper irreversibly to copper sulfide, which is the mineral, chalcocite. Silver sulfides, too, are minerals.

    Your experiement shows very clearly why you cannot "fix" coins that are corroded. The best thing you can do is to remove the corrosion, if it isn't too deep, and protect the coin from the atmosphere to keep it from reforming.

    Nature does not like the transition metals, and it converts them to minerals as fast as it can.
    Rob Woodside likes this.
  21. halford@thework

    halford@thework Junior Member

    How are those rainbow tones created by some eBay sellers? They list them as artificially toned, so are not trying to fool anyone.
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