Alexander Chalkos Bronze Disease Solution

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Author	Replies: 10 / Views: 2,115
imparatul New Member Romania 13 Posts	Posted 04/07/2021 04:19 am Hello, I have recently purchased this chalkos of Alexander that has what I presume is bronze disease. I would like to stop it from expanding if it's possible, so I'm asking for a solution to do this. Thank you very much! Report this Post to the Staff

echidna Pillar of the Community Australia 599 Posts	Posted 04/07/2021 06:23 am WD40 Watch your top knot Report this Post to the Staff
imparatul New Member Romania 13 Posts	Posted 04/07/2021 06:48 am Won't WD40 damage the coin? Report this Post to the Staff
echidna Pillar of the Community Australia 599 Posts	Posted 04/07/2021 06:57 am No it will not damage it. Watch your top knot Report this Post to the Staff
imparatul New Member Romania 13 Posts	Posted 04/07/2021 07:15 am Do I soak it? For how long? Report this Post to the Staff
echidna Pillar of the Community Australia 599 Posts	Posted 04/07/2021 08:14 am Soak the coin fully in WD40. Based on the images I'd say 30 minutes or so would do. If that's not enough then do it again. But experiment on one or two other coins first and you will get the idea. Watch your top knot Report this Post to the Staff
sel_69l Bedrock of the Community Australia 21788 Posts	Posted 04/07/2021 09:17 am Verdigris is a complex insoluble salt of copper hydroxycarbonate. The best way of passivating and removing it is to dissolve it. No severe mechanical tooling required. The chemistry of choice used by museums for the conservation and display of copper and bronze objects is to use a solution of sodium sesquicarbonate, where the copper in the verdigris is replaced by soluble sodium in solution from the sodium sesquicarbonate. Insoluble copper carbonate precipitates out. Sodium sesquicarbonate is difficult to buy, because it is semi unstable in air. However, is can be made by mixing the common and reasonably harmless household chemicals of baking soda and washing soda. Google for instructions on how the mixed solution is prepared and used. Some museums also preserve their treated coins with Renwax, which seals the surface of the coin, and prevents verdigris from starting again. Mainly used for ancient bronze coins, where the natural patina can vary greatly in color and darkness. Edited by sel_69l 04/07/2021 09:28 am Report this Post to the Staff
Seeker55 Pillar of the Community United States 634 Posts	Posted 04/07/2021 09:34 am Having used it successfully several times, I agree with the recommendation to use sodium sesquicarbonate, soaking the coin for a few days at room temperature Formula for sodium sesquicarbonate solution: 10.6 g of sodium carbonate (washing soda) and 8.4 g of sodium bicarbonate (baking soda) dissolved in 100 ml of distilled water Report this Post to the Staff
imparatul New Member Romania 13 Posts	Posted 04/07/2021 10:07 am Thank you very much for your answers! Report this Post to the Staff
louisvillekyshop CCF Advertiser United States 1304 Posts	Posted 04/07/2021 1:54 pm Well anything you react with the Copper might be useful to form a more stable salt that is less of a problem. Brown.edu says the following about chemical composition: --->"The actual chemical reaction is still not fully understood, though the chemistry of corrosion has been studied for some 150 years. However, the basic understanding of the process indicates that the presence of cuprous chloride in copper alloys reacts with water to create hydrochloric acid. The acid then eats away at the bronze, and in turn reacts with the copper. This second equation produces the visual manifestation of the disease: that dreaded green fuzz. Generally, the fuzz covers pockmarks caused by the hydrochloric acid."<--- +H2O ----> 2HCl + Cu2O 2HCl + 2Cu ----> 2CuCl + H2 A basic representation of the chemical process. There is a great presentation below for this: http://www.crescentcitycoinclub.org...0Disease.pdf So can you react the copper to something less horrible to deal with? Something more stable? Well notice they mention the sodium sesquicarbonate quite extensively but they also mention some fish tank cleaning chemicals as an alternative. They can have thiosulfate so you might pull the chloride off and do this: CuCl2 + Na2S2O3 ----> CuS2O3 + 2NaCl Thus you have choices..... Probably end up turning the coin black with the fish cleaning chemicals if you are not careful. So maybe clean out the spots and then q-tip applications into pits with drying? Citations: https://www.brown.edu/Departments/J...st/4867.html Edited by louisvillekyshop 04/07/2021 1:59 pm Report this Post to the Staff
imparatul New Member Romania 13 Posts	Posted 04/07/2021 2:46 pm Thank you! Report this Post to the Staff
	Replies: 10 / Views: 2,115

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