Bronze Disease - Coin Community Forum

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Author	Replies: 4 / Views: 1,052
echizento Moderator United States 23731 Posts	Posted 04/12/2007 6:12 pm Bronze Disease is a green or blue-green power like substance that can occur on bronze or bronze ally type coins. Bronze disease is dangerous and if not corrected will destroy the coin. This type of corrosion is mostly found on ancient coins but can also occur on more modern coins if the conditions are right. Cuprous Chloride which may be present in the coin reacts with moisture, sometime as little as what is in the air turn into Cupric Chloride and Hydrochloric Acid. This eats on the coin creating corrosion. It appears as a bright green or blue-green powder like substance and feels a soft fuzz. There are several ways of treating a coin with this problem. The simplest is to place the coin in a 250 degree oven for 30 minutes, which will remove any moisture in the coin. However more time than not the coin has to be treated with chemicals. This should only be done through a coin conservator and on coins of value. Here are two examples of coins with Bronze Disease. The first is a Roman AS of the Emperor Trajan, You can still see the green color and the damage that was caused by the problem. Luckily the problem has been corrected and the coin is no longer corroding. The second is a more modern English George V 1917 Penny. Somehow moisture has affected the right side the metal has become rough and pitted. I have removed most of the green substance, hopefully this will be enough. Image: b2.jpg 52.82 KB Image: b3.jpg 52.4 KB Image: b1.jpg 44.82 KB Report this Post to the Staff

EgCollector Pillar of the Community Egypt 3470 Posts	Posted 04/12/2007 8:20 pm nice information echizento, but is it a proper thing to do putting a coin in 250 degree oven for 30 minutes even if it has bronze disease? I dont know, thats why I'm asking. Report this Post to the Staff
echizento Moderator United States 23731 Posts	Posted 04/12/2007 8:57 pm This is a recommended process, it wouldn't damage the coin but it may change the toning slightly. Ron Report this Post to the Staff
EgCollector Pillar of the Community Egypt 3470 Posts	Posted 04/13/2007 3:59 pm Thanks for the info Ron Report this Post to the Staff
Conder101 Bedrock of the Community United States 17884 Posts	Posted 04/18/2007 7:22 pm Yes it would be proper because if the bronze disease is not stopped it will continue until the entire coin is destroyed. Consider this medical analogy. Say you have gangrene in your arm and it is spreading up to your shoulder. Now we can amputate, but you won't look as good (We can heat the coin in an oven but it may affect the toning), or we can not amputate and the gangrene will continue to spread and you will die shortly (we leave the coins alone and the bronze disease continues until all we have is a fuzzy green lump of corrosion). The first action is unpleasant to consider, but it is less objectionable than the second course of action. Report this Post to the Staff
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