Ring turns finger green

What is the actual chemistry involved in all the different situations where rings turn fingers green? Is the issue usually (always?) with copper? Anyone know of any research studies on the subject?

Janet in Jerusalem

It’s a copper oxide formation process. Your skin oil and sweat provides
the solvent to turn it into ink/dye.

I don’t think it’s a copper oxide, but rather (hydrated) copper chloride salts formed when sweat combines with the copper in the ring alloy.

The internet is chock full of guesses on this subject–something I am not looking for…:-)… I am looking for detailed answers regarding the actual chemistry. If someone wants to refer to ‘sweat’ or ‘lotions’, please give the relevant chemical compositions. Answers given so far do not take into account the fact that most rings which contain copper do not, as a rule, turn fingers green. A proper answer would first need to make a case for attributing the cause of the phenomenon to copper and then show the chemistry involved in the in various case scenarios. References to studies would be particularly helpful.

Janet in Jerusalem

Hi Janet,
your original post interested me, so I googled for the chemical composition of sweat. There were some useful answers, with actual values of individual chemicals, with the qualification that the specific composition depends on the individual’s chemistry.
Next I searched for metals turning fingers green, the answers referred mainly to copper, tho in sweat analysis many other metals were mentioned.
Re rings containing copper, ie standard sterling, in the moist saline oxidising conditions between finger rings and skin, anything can happen! despite there being only 7.5% copper therein.
I didnt find anything more specific than the above.
Surprisingly no guesses tho.

Hi Ted,

I consider anything that mentions sweat, lotions, etc. but doesn’t mention the particular relevant chemicals as guesses…:-)…

Janet in Jerusalem

"Copper(II) acetate is soluble in alcohol and water and slightly soluble in ether and glycerol. It melts at 115 °C (239 °F) and decomposes at 240 °C (464 °F). It can be prepared by reacting copper(II) oxide, CuO, or copper(II) carbonate, CuCO3, with acetic acid, CH3COOH. … "

"…Propionic acid (propanoic acid) is commonly found in sweat - propionibacteria break amino acids down into propionic acid. Propionibacteria live in the ducts of the sebaceous glands of adult and adolescent humans. Some people may identify a vinegar-like smell with propionic acid, because it is similar to acetic acid, which gives vinegar its sour taste and pungent smell.

Anyway, need to clean the offending item …LoL Funnily enough a vinegar and salt scrub will clean the verdigris / oxidation off the metal.

See also:

Hi Jules,

  1. As James Binion wrote in your second link, “to get any to form of verdigris on gold or silver alloys would need lots of copper, like more than 50% Cu in the alloy”. So general information on verdigris would not be relevant for most gold and silver jewelry.

  2. You haven’t given us a connection between propionic acid (propanoic acid) and greenness resulting from the wearing of gold or sterling silver jewelry.

  3. Any explanation attributing the greening phenomenon to copper would have to explain why the huge market of all-copper jewelry (generally claimed to treat a number of ills) does not cause greening of the skin for most people.

  4. Any explanation about the greening phenomenon would have to explain why relatively few people are affected. Obviously it has to do with individual body chemistry. My interest was spurred by mention of the problem arising for someone regarding a 14K gold ring (which would not have such an effect on the vast majority of folks).

This has been a very interesting discussion and some excellent explanations from members I admire for their expertise in metallurgy and hands on expertise.

I want to share an observation around 40 years old. I dated a woman who after her 2nd gin and tonic her skin on her fingers that had a gold ring on it would turn green without fail. Something in the tonic and/or gin changed her body chemistry to cause the reaction.

Rick Copeland

Hi Janet,
Since we’d all be guessing without spectroscopic analysis of the metal, the specific sweat and location (seafront air?) it’s a moot point.
No one can know what other chemicals are present.

I’d simply recommend washing more often! LoL.

I doubt this statement has been proven either " …like more than 50% Cu in the alloy".
according to Prof Dr Erhard Brepohl, up to 41.5% of the 585/1000 alloys can be copper in bright yellow gold.
With mixed alloys there is more likelihood of electrolysis leaching the reactive metal than with a a pure metal.

The two acids are very similar, and one of them is quoted at causing verdigris which is green. QED.

In practical terms, if I would make the person a ring in a higher carat gold maybe even 99% gold and 1% titanium. . It is hard enough.