Chemistry, verdigris

Is possible to find the answer to a simple question about the green or blue substance that grows on copper or bronze, know as verdigris (verderame).

What is the work of the verdigris? At first I thought that it is like decay for a tooth, that it exacavates inside and eats away the nugget, otherwise why it is not present in certain areas that are rounded? What happens to the resulting matter, if there are holes in the nugget caused by the verdigris what happens the matter because there is less of the mineral. Look at the photo and you see that where there is the verdigris the shape changes and goes in a hole. The verdigris doesnt yet cover the full of the nugget.

I have a supposition that there is a gas or atmosphere around the nugget when there is verdigris, and like a gas maybe interacting with certain bacteria or microorganisms that are invisble but have a link with light and gas and electricity. In my simple mind I cant find more questions.

(btw I had another nugget that was bought the same time, I managed to get it clean and dont remember how or either something occoured that cleaned it, since the nugget had disappeared for a few weeks two years ago. Still after long time the verdigris never appeared on this cleaned nugget. In springtime I donated that one to a young person that went travelling to Mexico.)

Isn’t the greenish substance that appears on copper just copper oxide? I think it’s an oxidation product resulting from the interaction of O2 and copper compounds. It’s sort of the copper equivalent of rust on iron.

Hi Nic. The verdigris maybe coexist with or near the oxidation but copper oxide is brown and grey, is caused by oxygen in the air, apparently after the initial film it does not corrode futher and it prevents further corrosion, iron rust corrodes with no end. The green substance on copper is acetate, a copper compound that is a salt.

The one in th photo I put it in a bleach detergent for a while with no noticeable changes, altought I felt the ‘cloud’ around the nugget was finished or maybe diminished. After i tried lemon juice and it immediately clean the where the copper is visible and made it shine. Now I put it in vinegar for 2 hours, and leaving it to dry.

According to website the verdigris is soluble in alcol and also in water

https://www.solubilityofthings.com/copper-ii-acetate
https://www.solubilityofthings.com/water/ions_solubility

I still cant remember how I manage to clean the other, it become perfectly clean in every cavity, I only registered that was clean when I found it again one morning on the kitchen floor underneath the cushions I lay to sleep one warm summer night, in the same spot I put it 2-3 weeks before.

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