How Long Does Verdigris Take To Spread?

Eric, I have wondered the same thing so have been trying an experiment. I took a couple of of coins with lots of verdigris and put them in a zip lock bag with a handful of copper cents and threw them in a desk drawer. they have been in there for a few months now and the last time I checked the unaffected coins were still unchanged. I will keep an eye on them and post if there are any changes.
Jim

It's also known as "bronze cancer", and like cancer, it can be unpredictable. It might sit there, mostly harmless, for years - then suddenly break out and start spreading. If the conditions of the coin change - say, the coins are poured out of one jar and into another, or the jar is moved to a different environment - can be enough to trigger the spreading.

It's also important to note that not all "green stuff" on coins is prone to spreading. Bronze patina is very dark green, and on ancient coins is stable, and even preferred to bare copper metal. A modern coin shouldn't have developed this yet, but under certain conditions a similar encrustation can form.

General rule of thumb: if it's dark green and glossy-looking, it's safe and stable. If it's pale green and/or powdery-looking, it's the bad stuff.

Very descriptive analogy Sap. Coin analysis is all about "eye" awareness and it is often hard to put in words, yet you have done an excellent job. Copper is a very reactive metal under the correct circumstances, such as when in contact with moisture and mild acids or bases (Ph). Minor long term exposure to chemicals tends to develop patina on the coins surface, where as specific moisture/chemical concentrations corrode the surface. Rarely would you see a copper coin with original patina that is less then 100 years old. Under the correct lighting conditions the 1832 Half Cent toning is luminescent green with virtually no pitting, where as the 1881 3CN's surface has been breeched.

1832 Half Cent


1881 Three Cent Nickel

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Minor long term exposure to chemicals tends to develop patina on the coins surface, where as specific moisture/chemical concentrations corrode the surface.

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Interesting. As an analogy it sounds like taking a little poison over a long period, one tends to develop a resistance to it, but a big dose at once kills.

Not that it is important but it is spelled Verdigris. And it is not actually Verdigris on your coins unless they were exposed to an Acetate such as what is in Vinegar. Many silly people clean coins with Vinegar and that could start Verdigris. Any coin containing Copper will start to turn to a brownish or greenish color as long as it is exposed to Oxygen, Carbon Dioxide and Moisture. Actually all Copper anything is effected similarly. Copper piping is an example. Underground Copper Grounding systems show that same reaction. No it's not PVC either. Another typical old wives tale, so to speak. Meaning a story repeated over and over and over and just becomes a habit instead of fact. Bronze, Brass, many coins contain Copper and they all react with O, then CO2 and then with H OH. The greenish coating you find on anything Copper is called Copper Carbonate noted as [CuCO3-Cu(OH)2].