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  • rickoricko Posts: 87,353 ✭✭✭✭✭
    edited April 30, 2018 5:40AM

    Good question... Having spent years in a plating industry, I know what they are when seen in gold plating operations, and I have seen them on modern copper plated cents. However, gold coins are not plated....not real one's anyway. Perhaps an expert can help with this one. Cheers, RickO

  • RogerBRogerB Posts: 8,881 ✭✭✭✭✭
    edited April 30, 2018 6:41AM

    "Occluded" means hidden. If gas bubbles (?) are hidden, then they are not visible.

    It is possible to have inclusions of slag copper oxide and other materials in a planchet. But they would be visible at the surface of a coin.

    In this era, a draw bench was in use for final normalization of DE strips. It seems extremely unlikely that any pocket of gas could survive rolling and drawing.

    [PS: The coin is not uncirculated.]

  • FredWeinbergFredWeinberg Posts: 5,285 ✭✭✭✭✭

    I don't see any raised occluded gas bubbles,
    and don't recall that coin....

    To me, that term means raised bubbles, not
    lamination flaps or strips. I don't see those.

    ????

    Collector & Dealer in Major Mint Error Coins & Currency since the 1960's.Co-Author of Whitman's "100 Greatest U.S. Mint Error Coins", and the Error Coin Encyclopedia, Vols., III & IV.
    Authenticator for Major Mint Errors
    for PCGS. A 42 +-Year PNG Member, and an ICTA Board Member.A full time coin dealer since 1972.
  • RogerBRogerB Posts: 8,881 ✭✭✭✭✭

    Maybe someone at the TPG was doing a crossword puzzle....or playing scrabble? ;)

  • CascadeChrisCascadeChris Posts: 2,495 ✭✭✭✭✭

    @FredWeinberg said:
    I don't see any raised occluded gas bubbles,
    and don't recall that coin....

    To me, that term means raised bubbles, not
    lamination flaps or strips. I don't see those.

    ????

    Fred. I sent a Morgan in with an occluded gas bubble and it was just called a "minor lamination" so I assumed they just used that as a blanket term for label space...



    The Blind VAMmer
  • FredWeinbergFredWeinberg Posts: 5,285 ✭✭✭✭✭

    That one (above) should have been
    called an occluded gas bubble.

    Collector & Dealer in Major Mint Error Coins & Currency since the 1960's.Co-Author of Whitman's "100 Greatest U.S. Mint Error Coins", and the Error Coin Encyclopedia, Vols., III & IV.
    Authenticator for Major Mint Errors
    for PCGS. A 42 +-Year PNG Member, and an ICTA Board Member.A full time coin dealer since 1972.
  • Insider2Insider2 Posts: 14,457 ✭✭✭✭✭

    @RogerB said:
    "Occluded" means hidden. If gas bubbles (?) are hidden, then they are not visible.

    It is possible to have inclusions of slag copper oxide and other materials in a planchet. But they would be visible at the surface of a coin.

    In this era, a draw bench was in use for final normalization of DE strips. It seems extremely unlikely that any pocket of gas could survive rolling and drawing.

    [PS: The coin is not uncirculated.]

    I think the term came about because any "gases that became trapped as the "pour" solidified" were not seen. It was not until something caused the gas to migrate to the surface (in most cases heat or an atom smaller than the other atoms in the coin's alloy) that a bulge appeared on the coin's surface. When that become visible, we called it "Trapped Gas" or "Occluded Gas." AFAIK, this has not changed since the '70's. As an authority on the minting process, perhaps you can come up with a better term for modern collectors.

    BTW, round "bubble-like" characteristics as this can occur on cast coins. The difference is the cast "bubbles" are solid while an "occluded gas bubble" will press out.

  • CascadeChrisCascadeChris Posts: 2,495 ✭✭✭✭✭
    edited April 30, 2018 10:41AM

    @FredWeinberg said:
    That one (above) should have been
    called an occluded gas bubble.

    Thanks Fred. I'll bring her to LB in June. Maybe you can have her fixed for me. It must have been one they just didn't send you rather than my assumption of using a blanket label-space term. I know its not too large but occluded glass bubbles on morgans, or alloyed coins in general, isn't too common so I would like it to be correct.

    The Blind VAMmer
  • FredWeinbergFredWeinberg Posts: 5,285 ✭✭✭✭✭

    I'll be glad to re-write it up for you
    on a form there.

    Collector & Dealer in Major Mint Error Coins & Currency since the 1960's.Co-Author of Whitman's "100 Greatest U.S. Mint Error Coins", and the Error Coin Encyclopedia, Vols., III & IV.
    Authenticator for Major Mint Errors
    for PCGS. A 42 +-Year PNG Member, and an ICTA Board Member.A full time coin dealer since 1972.
  • RogerBRogerB Posts: 8,881 ✭✭✭✭✭

    Insider2 et al....Yea, I see the surface defect on the Morgan dollar, but not sure how to objectively characterize it, or even of the cause. A bubble of trapped gas, especially of the size on the Morgan, would never survive ingot rolling and other processes. But, I don't know what caused the one illustrated. (Maybe CascadeChris will consider allowing me to examine the coin at some time.)

    On the OP's coin, I don;t seen anything in the photos.

  • Insider2Insider2 Posts: 14,457 ✭✭✭✭✭

    The coin starts out normal. Then the atoms migrate. Cast silver is very susceptible to oxygen contamination. Hydrogen and Oxygen atoms are also smaller than Silver atoms. Over time, these atoms can migrate toward the surface. Heat, speeds the process. Take a torch to a clad coin and watch what happens.

    If Chris wishes to ruin the coin, he can put his fingernail on the bump and press.

    As for things surviving the rolling process... all kinds of crap gets rolled in, Many laminations are caused by debris or trapped gas.

  • RogerBRogerB Posts: 8,881 ✭✭✭✭✭
    edited April 30, 2018 2:14PM

    A clad coin and a silver alloy coin are entirely different critters.

    RE: "The coin starts out normal. Then the atoms migrate."
    Nope. The migration scale would have to be enormous in order to produce the slightest visible blister.

    Atomic H and O have no impact on coinage alloy or on formation of "gas bubbles" in struck coins. Silver would naturally segregate in coinage melts which is why assayers averaged measurements from ingots. Excessive mixing, though, increased copper oxide.

    Free H and O are nearly always in diatomic molecules, and they are rarely free within a silver-copper melt. During melting and casting any dissolved O2 will be absorbed in the flux or combine with Cu into the oxide. This was called "fire scale" and was a common inclusion in silver and sometimes gold strip.

    Solid debris can be retained or exposed throughout the rolling processes. Not gas.

    Please consult a practicing professional metallurgist, as I did, to understand what does and does not happen outside of the fantasy world of numismatics. :)

  • rickoricko Posts: 87,353 ✭✭✭✭✭

    Anomalies seen by collectors are often incorrectly labeled since collectors are rarely metallurgists. For example the recent (and often repeated) thread about 'sintered' nickels. While I do not have a degree in metallurgy, I have taken courses in the subject and worked with metals (plating, forming, heat treating and machining) throughout my career. We try to correct some of these misnomers when the topic comes up, however, they are so common in the hobby it is difficult to correct. Cheers, RickO

  • BuffaloIronTailBuffaloIronTail Posts: 5,910 ✭✭✭✭✭

    This dissertation is a little out of my realm. Very interesting stuff posted, though.

    The technical stuff has occluded me, though.

    Pete

    "I tell them there's no problems.....only solutions" - John Lennon
  • jwittenjwitten Posts: 4,907 ✭✭✭✭✭

    Here is my recent submission result from ngc. I've never seen a double lamination like this on gold, I thought it was pretty neat.


  • Insider2Insider2 Posts: 14,457 ✭✭✭✭✭

    @RogerB said:
    A clad coin and a silver alloy coin are entirely different critters.

    RE: "The coin starts out normal. Then the atoms migrate."
    Nope. The migration scale would have to be enormous in order to produce the slightest visible blister.

    Atomic H and O have no impact on coinage alloy or on formation of "gas bubbles" in struck coins. Silver would naturally segregate in coinage melts which is why assayers averaged measurements from ingots. Excessive mixing, though, increased copper oxide.

    Free H and O are nearly always in diatomic molecules, and they are rarely free within a silver-copper melt. During melting and casting any dissolved O2 will be absorbed in the flux or combine with Cu into the oxide. This was called "fire scale" and was a common inclusion in silver and sometimes gold strip.

    Solid debris can be retained or exposed throughout the rolling processes. Not gas.

    Please consult a practicing professional metallurgist, as I did, to understand what does and does not happen outside of the fantasy world of numismatics. :)

    You must be correct but I choose to rely on that "numismatic fantasy" as explained to me at the U.S. Mint's Department of Technology (Mint Lab) in the 1970's. They are the folks who tested all our coinage at the time. Perhaps Dr. Hunter is still alive.

    BTW, your excellent comments of why it is impossible to have any kind of gas "trapped" inside a finished coin is possibly why ALL OUR COINS ARE NOT FULL OF BUBBLES. :)

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