Humidity and Gold Storage

Discussion in 'Coin Chat' started by Coin Pedant, Jul 22, 2019.

  1. Coin Pedant

    Coin Pedant Member

    Are gold bullion coins affected by humidity? Does it cause physical damage to the surface?
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    GDJMSP Numismatist Moderator

    Yes, but at a much slower rate than it does other metals - as a general rule.

    Contrary to popular belief - gold tones.
    Paul M., imrich and Coin Pedant like this.
  4. Coin Pedant

    Coin Pedant Member

    Is this what forms the copper spots and surface damage? I am unsure where the line between toning and surface deterioration starts and ends. Does toning lead to damage or protect the surface?
    Many thanks
  5. Johndoe2000$

    Johndoe2000$ Well-Known Member

  6. nuMRmatist

    nuMRmatist Active Member

    I remember from Chem in college that WATER self-ionizes into some H3O's (acid), and OH (base). (I'm amused at bottles of water marketed as 'De-Ionized Water)...

    As far as gaseous water - humidity, and Gold being oxidized there-by, hmmm.......
  7. Paul M.

    Paul M. Well-Known Member

    @GDJMSP is right, of course. Gold tones. But, as long as you don't store it in your bathroom, anywhere that's comfortable for humans to sit for long periods of time is probably good enough for your gold coins.

    GDJMSP Numismatist Moderator

    Yes, yes, and yes.

    Confused yet ? :)

    Well don't be, the answer to all of your questions is indeed yes. Now some might say it can't be, but it is. It's your other comment -

    - that provides the explanation, once one understands it. It's that line you're talking about. Ya see, from technical perspective all toning is damage because toning is the corrosion of the metal and corrosion cannot ever be anything but damage. But, as collectors, we don't see it that way for when toning is attractive to our individual eye we see that as being a good thing - not a bad thing. However, as toning progresses to certain degrees metal is actually destroyed and the coin left pitted with the surface actually eaten away.

    So if that's the case how can toning be destructive and protective at the same time ? Well, it isn't always, but under certain circumstance it is. Ya see, in the beginning stages toning starts because very fragile, reactive metal is exposed to the forces of corrosion in the form of luster. And it is that fragile metal that tones first. This part happens rather quickly. But once it's begun, and the most fragile parts of the metal are toned, it then takes longer for the underlying metal to tone. So it is in that way that toning on the top layers protects the underlying layers of metal. But, the toning is still progressing, just at a much slower rate.

    And of course toning is all dependent upon the environment, change the environment and you change the rate at which toning progresses. So a lot of people think it's the initial toning that has slowed things down and is protecting the coin when it is actually changes in the environment that did it.

    To help understand it better, visualize it like this. This is the luster on a coin -

    Now at the peaks only a single tiny molecule of metal is exposed - that is the most fragile part because it only touches other metal directly underneath - all other sides are exposed. It's like a single tiny - . - (period) sitting right on the very top. As you progress down the sides of the incline into the valley other metal is exposed, but it is protected by other metal on all sides except at its very top - so only the very top of that tiny . (period) is exposed to the air. So, one tiny point of a period exposed, as compared to one tiny point of a period protected. And once you get past those tiny periods, all the other metal beneath is protected - by the metal on top of it.

    Once you visualize it that way it becomes a lot easier to see and understand the toning process.
    Coin Pedant likes this.
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