Featured Verdigris....Make your own solution to eliminate this ugly corrosion

Discussion in 'Coin Chat' started by Greg Clark, Nov 9, 2016.


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  1. Greg Clark

    Greg Clark Member

    Verdigris is the name for that green stuff that gets on improperly stored copper coins.
    There are several 'over the counter' remedies you can buy but the best thing is to understand the chemistry of verdigris and how to use chemistry to fix it.

    You do NOT need any chemistry knowledge to make the solution and combat this nasty chemical reaction.

    Before getting into the weeds on this subject let me qualify my diagnosis and the solution to this problem.
    I am a chemist and understand the chemical processes that takes place over time which produces verdigris. I also understand the process to correct it's destructive properties.

    I must tell you that this process can take up to several weeks to complete. That should not come as a surprise since it probably took many years for the reaction that produced this nasty green stuff.

    First of all you DO NOT need to scrape, brush or otherwise clean the surface of your coins before doing this treatment. If you have nice coins of high value that are just starting to get this disease you will be able to stop it in it's tracks and restore the look of your coin. If you have coins that are beyond surface 'fuzz' you will be able to stop the reaction and neutralize the verdigris but if the verdigris had the chance to eat away at areas of the coins surface you will see the resulting pits. Your results will be a coin with rough surfaces and if the damage is bad enough it will be pitted or worse.

    I have used this treatment on many coppers and submitted them for grading to NGC and PCGS. The results were as I would have suspected. On coins that only had surface fuzz on them they were graded without any negative attributions. The coins that were mildly corroded received grading with notes of 'rough surfaces' and some received details grades with note of 'cleaned'. The worst all had details grading with most receiving the note 'environmental damage'.
    At any rate, many of these coins would have been returned in body bags had they not been treated first.

    The treatment I am about to disclose is the same treatment used by all good coin preservation companies and how they treat verdigris. The best way to fight against this chemical reaction is to use chemicals to reverse it. It's by far a better choice than any other I've seen or tried.

    Here's the simple solution and how to make it.


    A simple scale accurate to 1/0 gram.

    Baking soda (arm and Hammer is best for purity)

    Soda Ash (Washing Soda....Arm and Hammer washing soda is pure soda ash)

    Distilled Water (DO NOT USE TAP)

    glass container.

    That is all you need.

    Fighting Acids with Bases.....Sodium Sesquicarbonate..

    Don't have sodium sesquicarbonate lying around? You can make it
    with equal molar amounts of sodium carbonate (also called soda ash) and sodium bicarbonate (Baking Soda). For example, a 5% molar solution would be 10.6g of carbonate and 8.4g of bicarbonate in 100ml of water.

    You do not need to be spot on with the amount of water. 100 ml is one tenth of a liter. You can figure it roughly and be fine.

    Now understand the simple relation of molar strength (don't be concerned with this technical language) to the above formula. If the weight of the chemicals remains the same and you double the amount of distilled water you will go from a 5% solution to a 2.5% solution. On coins with nice tones you will want to use the less concentrated solution to avoid removing tones. I recommend using 1% solutions to avoid all possible problems. Understand the times required to treat the coins extends exponentially.

    Place the coins in a glass container and fill with a 5% solution (toughest cases) of sodium sesquicarbonate. Let them soak for about 14 days, replace the solution, and soak for another 14 days. Then, place the coin in distilled water for about a week.
    A 5% solution WILL REMOVE any "patina" on the coin! If there is an exceptionally aesthetic "patina" to be preserved, try a 1% or 2% solution. Be warned, though, that it will take three times as long, and has a higher risk of being ineffective.

    Now you have all the information you need to treat verdigris. The time of 2 weeks with new solution and another two weeks are for the worst of the worse. Experiment on none precious coins until you get the desired results. Try the 1% on a coin with toning and try 5% on a different coin with similar tones and see what it does.

    Play around with it....have fun....you are now a professional copper coin preservationist.
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  3. Stevearino

    Stevearino Supporter! Supporter

    Will experiment, thanks for the lesson.
    Greg Clark likes this.
  4. rickmp

    rickmp Frequently flatulent.

    Stepping on @BadThad's toes.
    I'll trust VerdiCare. Your recipe is much too complicated for someone who doesn't have a degree in chemistry.
    And what does 'A simple scale accurate to 1/0 gram.' mean?
    What is a molar solution? Toothpaste?
  5. Greg Clark

    Greg Clark Member

    You don't know what a scale is?
    You think this is complicated?
    Stick with what you know....not sure what that may be but stick with it...
    1776 and Insider like this.
  6. Stevearino

    Stevearino Supporter! Supporter

    Molar weights aren't a factor; Greg has already calculated them for us. And since he mentioned it didn't have to be "spot on" it's worth at least experimenting on some non-valuable stuff (which most of us probably have sitting around).
    Greg Clark and Insider like this.
  7. Insider

    Insider Talent on loan from...

  8. Greg Clark

    Greg Clark Member

    A correction is needed brought to my attention by rickmp
    The scale should be accurate to .1 grams, 1/10 not 1/0
    Insider likes this.
  9. rickmp

    rickmp Frequently flatulent.

    I know what a scale is. What does 'accurate to 1/0' mean?
    Your first post here and you get an attitude because I don't know what you're talking about? Blocked.
  10. Insider

    Insider Talent on loan from...

    :yack::yack::yack::yack::yack: :vomit: :rolleyes: :facepalm: :bigtears::bigtears::bigtears::bigtears::bigtears:
  11. SuperDave

    SuperDave Free the Cartwheels!

    No, we already have a proven solution developed by a chemist and tested over many years. Why do it from scratch?
    jester3681 and RonSanderson like this.
  12. RonSanderson

    RonSanderson Supporter! Supporter

    And I get to give @BadThad a pittance for buying some, but a lot of appreciation for helping me save some coins for posterity.
  13. BadThad

    BadThad Calibrated for Lincolns

    Collectors of ancients have been doing this for decades. It does work but it will also ruin the patina.
    rickmp likes this.
  14. Insider

    Insider Talent on loan from...

    :( Wish I had your knowledge of chemistry. Then I could have checked the "No help at all" option above." :smuggrin: Anyway, I was glad to see you agree with the OP who warned us already about the issues with a coin's patina. I'll bet in many cases two chemists are better than one.

    BTW, I just posted on the ancient forum to see if any collectors have tried your product. Look at it as free advertising. ;)
    Greg Clark likes this.
  15. Greg Clark

    Greg Clark Member

    This method does not require rubbing or cleaning the surfaces and if you have a valuable coin this is imperative.
    Also, you can restore many hundreds of coins for just a few bucks.
    Don't try it....do try it....it's up to you. I know those who will try this will not go back to anything they have tried before. This works every time and costs a few pennies per coin.
    Stevearino likes this.
  16. SuperDave

    SuperDave Free the Cartwheels!

    Oh, I quite intend to try it. :)

    I don't know you, obviously, but I've known Thad for years and his endorsement of your method is good enough for me. And any chance to do conservation the slow way is a good chance for me. :)
    Insider and Greg Clark like this.
  17. GDJMSP

    GDJMSP Numismatist Moderator

    As rickmp said the product is called VerdiCare.

    Verdicare does not require any rubbing or cleaning either, nor does it ruin the patina of the coin.

    Based on your comments is appears to me that you are at the least unfamiliar with it and perhaps even totally unaware that Verdicare even exist. So I'm going to make the same suggestion to you that you are making about your method - why don't you get some and try it. I think you'll be in for a pleasant surprise because it works rather well.
  18. RonSanderson

    RonSanderson Supporter! Supporter

    Greg, upon reviewing my comment above, I wanted to make sure it did not sound dismissive of your contribution. The more good ways to save a coin, the better!

    I did post some before / after pictures of one coin I treated using VerdiCare, in this post in the Post your Lincolns thread: #3830. My pictures aren't the best, and the coin looks a little extra glossy because it hadn't entirely dried yet. But you might find them interesting.

    I think @SuperDave hit just the right note in his reply, where I may have fallen a bit short. Best regards!
    Stevearino, Greg Clark and Insider like this.
  19. Greg Clark

    Greg Clark Member

    Use the 1% solution and it will not remove toning. The patina you are speaking of is the green patina that is common on bronze. It will remove that at any strength.
    I could show the reaction(s) that take place to produce the green patina and what takes place to make it acidic and how to combat these but it goes well beyond the scope of a forum such as this.
  20. Greg Clark

    Greg Clark Member

    I have used VerdiCare and Verdigone. Not the same as this.
  21. Greg Clark

    Greg Clark Member

    Reading the post and seeing the scale is used to weigh chemicals to .1 gram should have told you 1/0 was a typo.
    Insider likes this.
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