Featured Homemade Verdigris formulas

Discussion in 'Coin Chat' started by GSDykes, Jan 26, 2020.

  1. GSDykes

    GSDykes Well-Known Member

    Herein I hope to post various types of homemade "verdigris" solutions. I begin with a post from a chemist; in 2016 on CoinTalk® (!?) Greg Clark posted this formula, for a Verdigris-like compound:

    "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.

    Greg Clark, Nov 9, 2016 Report
    #1 Like + Quote Reply"

    Has anyone tried this formula?? I will try to post others as I find them.
    Gary in Washington
    Beefer518, Pellinore, seth77 and 5 others like this.
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  3. GSDykes

    GSDykes Well-Known Member

    Adapted from a Coin Community post, a test using heated Olive Oil (use cold pressed virgin):

    After years of experiments in conservation in copper coins this is my opinion. Green vedigres can be stopped even with aggresive or non aggressive methods. Warning the patina can be lost via this method. So, experiment. Heating the virgin oil in saucepan is fairly aggressive, compared to lukewarm soaking, below.

    Non-heated virgin olive oil is not aggressive but does have some disadvantages. Put the coin in a glass of oil and you will see after 2 days the oil will change color. Absorb and stop the verdigre but the color of the coin will be a little a bit darker than it was.

    Stopped green vedigris but became darker. Also some spots remain were it was green. But of course much much better than it was before.

    end of adaptation, has anyone tried this??
    Gary in Washington
  4. GSDykes

    GSDykes Well-Known Member

    From "topcoins.com" comes this information:

    "On cleaning coins with verdigris: you first need to have your coin clean of any wax or oil product particularly preservatives. The verdigris is a chemical reaction occurring between the moisture in air and the coins surface. This chemical reaction eats into and destroys the coins surface.

    I have had great success in removing verdigris from some of my prize specimens using Benzotriazole 5% in Ethanol. (Which is flammable and only to be used out side in open air with eye protection). It took longer then I had expected but I am pleased with the results and I have not damaged the patinas.

    I have read that some patinas have been harmed using this product but so far that is not my experience. When your coin is clean of verdigris, anywhere from a week to some months depending on the depth of the reaction, the coin must be soaked in distilled water for at least a week but a month would be better.

    Your coin is then dried in air and then in an oven, to drive out any entrapped moisture. The oven should only be moderate heat about 200 F or 140 C. Leave it to dry in the moderate oven at least 10 to 15 min. remove and cool to room temperature slowly. Apply Ren wax or Lanolin oil to the surface to seal it from the elements."

    end brief quote,

    interesting, I wonder where one can purchase this stuff??
    Gary in Washington
  5. GSDykes

    GSDykes Well-Known Member

    A brief selection from www.buriedtreasurehunter.co

    "There are a range of oils or solutions that can be used or made up which I will list shortly but let’s first discuss why it works.

    The oils and solutions work because they are acidic in nature and [​IMG]will gradually break down, soften and remove corrosion or verdigris. Some oils and solutions are more acidic than others so in some cases you could leave a coin in a solution for a couple of days and in other cases you may only want to leave it for a few hours. Soaking is a slow process and sometimes may take weeks! Regular checking is the key because if you forget about it, there’s no going back!

    What works is the acidic fatty acids and they do the work but it must be remembered that even though it’s mild and slow acting, it is corrosive and they can eventually etch into a coin or artefact if left unchecked or unwashed and neutralised afterwards.

    It can be helpful from time to time to check on items being soaked and help it along by removing it and gently working a wooden toothpick or wooden sweetcorn skewer into it to remove any larger deposits before returning it to the solution.

    (I recently saw the huge difference soaking had made to a silver coin found on a club site. Quite a rare Oliver Cromwell Commonwealth Half Crown in fact!)." END

    Again experiment with low value items,
    Gary in Washington
  6. GSDykes

    GSDykes Well-Known Member

    A quote from www.hunker.com:

    Mineral Oil
    Step 1

    Fill a cup with mineral oil or olive oil. Either one is viable for removing corrosion from coins. The oils contain trace minerals that loosen dirt and corrosion on metal coins.

    Step 2
    Place the coin in the cup. Allow the coin to soak.

    Step 3
    Remove the coin after the corrosion has fallen away. This can take several weeks.

    Step 4
    Rinse the coin using clean (i.e. filtered distilled water). Remove the oil using a soft, clean cloth.

    Step 5
    Pat down the coin with baking soda and rinse again. Baking soda neutralizes the minerals present in the oils and prevents them from doing long-term damage to the coin.

    Gary in Washington
  7. GSDykes

    GSDykes Well-Known Member

    A partial quote from classicalcoins.com:

    Conservation Measures

    Time: An Essential Ingredient

    The chlorides causing bronze disease pervaded the specimen over hundreds or thousands of years, and they won’t leave instantly. Treating bronze disease is a time-consuming process – no quick "solution" will leave the specimen relatively intact. Electrolysis (like other “quick fixes) inevitably leads to recurrence of corrosion and ultimate disaster. To do the job right and prevent recurrence, one must be vigilant, knowledgeable and patient - in some cases, it may take a year or more to stabilize the specimen.


    The least invasive countermeasure to halt progression of bronze disease is dessication - removing water needed to sustain the corrosion reaction. Baking at 250 degrees for at least 30 minutes does that. Once the specimen cools, water vapor in the air may be absorbed and act to restart the reaction. If the specimen is instead placed in an airtight container with a moisture absorbent such as silica gel, it will be safe until further conservation can begin.

    It has been reported that such heating may tend to darken a coin’s patina. Thus, it is best not to exceed 250o F during dessication.

    Treating Incipient Cases

    In cases where bronze disease is beginning to appear, soaking the specimen in distilled water (NOT chlorine-containing tap water) may suffice. Since moisture is needed to start the reaction, soaking in water may seem counter-intuitive. However, distilled water attracts chloride ions resident on or within a coin into solution, gradually removing them from the coin. As the water becomes saturated with chloride ions its effectiveness in removing chlorides diminishes, so changing the water periodically is necessary. The water should be changed every few days at first, and then weekly. Periodically check progress by drying the coin and examining it. Repeat the soaking as needed. In many cases, this is all that will be required to stabilize the specimen.

    Treating More Advanced Cases

    Sodium Sesquicarbonate Immersion

    1) Open up every pore site where bronze disease is progressing with a toothpick or (very carefully) with a steel needle, so that the solution can penetrate to the corrosion sites. It is permissible to remove corrosion products for appearance reasons, although that does not additionally contribute to halting bronze disease. Dessicate the specimen.

    2) During dessication, if made-up solution is not already on hand, prepare a 2% (by weight) aqueous solution of sodium sesquicarbonate in distilled water. If one doesn't have easy access to sodium sesquicarbonate, it can be made up from equal molar quantities of sodium carbonate (or soda ash - Na2CO3) and sodium bicarbonate (NaHCO3). A 2% solution would dissolve 4.24 g of sodium carbonate and 3.36 g of sodium bicarbonate in 100 ml of distilled water.

    Although many conservation authorities recommend a 5% sesquicarbonate solution, this strength will strip the patina from a specimen. The weaker 2% solution takes three times as long (and may be ineffective), but the reaction is slowed enough to allow monitoring and ending the soak before the patina is stripped. Use a 5% solution only if the 2% solution fails to stabilize, and if the conservator is prepared to accept a stripped specimen. Otherwise, repeat the distilled water soak and 2% sesquicarbonate solution immersion as many times as is required to stabilize the specimen.

    3) Place the specimen in a covered glass container (a Petri dish is suitable, as is the 8 oz. “jelly jar” used by home canners), and fill with a 2% solution of sodium sesquicarbonate until the specimen is well covered. Soak for two weeks, replace the solution, then soak the specimen for another two weeks or until a greenish color begins to appear in the solution - indicating that the patina is beginning to dissolve. Rinse the coin thoroughly in tap water.

    4) Soak the specimen in distilled water for 24 hours. Dry, then perform a silver nitrate test per Testing For Chlorides With Silver Nitrate . Use this procedure: “To Test for Chlorides in Objects Not Yet in Treatment.”

    5) If necessary, repeat steps 3) and 4) until the silver nitrate test is negative. Dry the specimen thoroughly. Do NOT seal its surface with lacquer or wax.

    Chlorine ions have now been removed from its surface. If the specimen is kept in a dry environment, bronze disease should not recur.

    Treating Serious Cases

    Additional steps for preventing recurrence of bronze disease normally are only necessary for objects that cannot be kept in a dry environment, or are internally pervaded by chloride ions. Do not attempt such treatment unless safety precautions for handling toxic materials are understood.


    Specimens subjected to conservation measures that improve their appearance (e.g. coins pitted by bronze disease) may not ethically be sold without full disclosure to the buyer. Classical Coins will not acquire or sell any coin whose appearance has been improved by such measures.
    end partial quote

    note the final warning!!
    Gary in Washington
  8. GSDykes

    GSDykes Well-Known Member

    Anyone try SAFECLEAN ??

    Our new non toxic, non acidic, non caustic, non corrosive, non irritating, non abrasive and completely biodegradable coin cleaner. It is not a "quick dip" type cleaner.
    Convenient ready to use formula.
    Gently, Predictably, Quickly and Safely soaks most silver and copper coins clean in minutes.
    SafeClean Coin Cleaner Concentrate 4 fl. oz.

    I have not tried it. Simply search to find it on-line.
    Gary in Washington

  9. GSDykes

    GSDykes Well-Known Member

    A partial quote from Collectorscoins.com

    For all my Dug Copper I use a Potato.......Cut a potato in half then

    1a) put the coin between the halves and rubberband the halves together tightly.

    1b) Make a small slit in the potato and insert the coin then rubber band the slit shut( kinda like a butterfly bandaid)

    2)Let set for length of time. Check periodically The gunk should just fall off.....may need a bit of assistance.

    Of course don't be doing this to $1000.00 coins.


    P.S. This is how I clean my dug copper coins....Use at own risk.
    end quote

    Gary in Washington
  10. GSDykes

    GSDykes Well-Known Member

  11. -jeffB

    -jeffB Greshams LEO Supporter

    OK, I'm curious about this, and here's one of the first links my search turned up:

    New Safeclean coin cleaner AARRRGGG! — Collectors Universe

    There's a fair amount of panic in the thread about the cleaner being acid-based -- but I think that's just a misinterpretation of the MSDS (Material Safety Data Sheet) for plain emu oil, found on the company's website.

    Emu oil is an animal oil, and all animal oils (fats) consist of triglycerides -- a compound of glycerin and organic acids. To describe an animal (or vegetable) oil chemically, you specify which organic acids go into the compound, and in what proportion. But they aren't acids any more when they're in the compound. Part of the acid combines with part of the glycerin, and the product is an oil that isn't acid at all.

    On the other hand, oils can break down in ways that free up those acids, or they can be produced in a way that brings along some unreacted acid. This is a particular problem in some vegetable oils, like olive oil; that's why an olive-oil soak can damage some coin surface if done for too long.

    The problem is that Safeclean's manufacturer apparently has NOT posted the actual product's MSDS anywhere, so we don't know whether what it contains is harmful to coins or not. Given that, I certainly wouldn't jump to try it on a valuable coin. Even if I tried it on some low-value coins with no apparent problems, I'd be reluctant to keep using it without knowing what's in it -- or without someone I trust telling me that its components are harmless.
  12. -jeffB

    -jeffB Greshams LEO Supporter

    BTW, thanks for starting this thread! A lot here to digest. (Pun intended, I guess; in chemistry, "digest" means to break a substance down by heat and/or soaking in chemicals!)
    Kentucky likes this.
  13. -jeffB

    -jeffB Greshams LEO Supporter

    I also hope @BadThad will weigh in here at some point. His excellent product, VerdiCare, has been used for years to remove verdigris and preserve copper coin surfaces, but it's now very hard to get. I'm hoping at some point he'll comment on the product's future. Regardless, though, he's a metallurgist, and knows a lot more about these topics than I ever will.
  14. GSDykes

    GSDykes Well-Known Member

    Yeah he had a product Verdigone, now Verdicare. I do not know why he is unresponsive, perhaps her had a stroke?
    Gary in Washington
  15. desertgem

    desertgem MODERATOR Senior Errer Collecktor Moderator

    Jeff, search this word document on the web:
    MSDS SafeClean

    PART No.: Non-toxic & Anti-static CLEANING - PROTECTING TREATMENT. SUPPLIER: Connector B.V.. A. Hofmanweg 55. 2031 BH Haarlem. The Netherlands.

    But it sounds as inert as water to me.

    Also, Thad was on a day or so ago. He is the expert and I wish he could finish his book on the subject as it would be a coin best seller. I am a #1 fan of verdi-gone and verdicare, and still have some. It also removes age spots off of numismatists skin and other good things :) just kidding on that. Jim
    Kevin Mader likes this.
  16. -jeffB

    -jeffB Greshams LEO Supporter

    I don't believe that's the same product. I came across another SafeClean that was a boiler descaler, I think. I don't have time to retrace my steps just now; I'll try to remember to check later.
  17. desertgem

    desertgem MODERATOR Senior Errer Collecktor Moderator

    Hi all, I have heard from Thad and he very much appreciate the feedback and wishes he could readily provide more of his efforts, but like all of us, Life often alters our plans. Not to say anything specific, he is very tied up with real life and new responsibilities. At the moment production doesn't seem to be feasible. The product was simply too good and demand overwhelming, and if/when he can resume, I am sure the positive demand will continue. Treasure what you have left , if any. IMO, Jim
    Kevin Mader and LakeEffect like this.
  18. barsenault

    barsenault New Member

    Hi there. I wanted to 'restore this' but not damage it. I'd like to get it graded without 'damage'. Any possibility of that happening? Anyone know the best solution to remove the issue on bronze. It is a rare Wiener medal. Thanks.


    Attached Files:

  19. LakeEffect

    LakeEffect Average Circulated Supporter

    That looks like a good candidate for Verdicare, unfortunately it's not available. You may want to check out the Ancient forum for tips on bronze disease, they are pretty knowledgeable on treating green stuff. Welcome to the forum!
  20. jafo50

    jafo50 Active Member

    I think that spot is going to be tough to remove and if you're successful the surface underneath the spot will probably look very different then the rest of the metal. Some grading companies offer conservation services but I'm not sure if they would conserve and grade this medal.
  21. barsenault

    barsenault New Member

    thanks for the help and guidance. I understand that there may be a spot left. I'm okay with that. I don't want to waste time and money to submit for conservation, if they're not even going to grade it. I'd rather attempt to do something myself, and maybe over time (many years), it will blend a little better. For those who are familiar with bronze, is it better to use the Olive Oil technique described above or Sodium Sesquicarbonate process described above. I'm assuming the 5% solution is the way to go? Or should I start with the 2% IF the SS is the way to go? Thanks
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