Hello all. I've recently been seeing more and more minor russian coppers with a strange appearance. They have grainy surfaces, are bright and shiny (but not in a good way) and look like they've been heated/scorched, Below is an example along with one I'd consider normal.

Comments?

Thanks

Strange
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Normal
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First one looks like it was dipped in a caustic cleaning solution.

My opinion is that it is a new method of chemical cleaning. All oxidation is removed with acid, then the rough surface is smoothed a bit. Maybe even heat is applied for that purpose.

Another example

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I would agree with Art about the acid or other reactive agent -- it also looks like it was scrubbed with a wire brush!
As to the shiny appearance, it could be lacquer. Here is one of mine which I think has been lacquered: L I N K

These look like some Ekaterina's that I bought about 6 yrs ago, that were harshly cleaned, I think I got them for $3 each.

Hi Steve, someone has tried to remove verdigris. I obtained the same ugly look years ago when soaking oxidized copper coins. I do not recall whether it was with ammonia solution or hydrochloric acid. The verdigris went away but it had, of course eaten into the surface of the coin - leaving wounds. Brushing did not improve much.
If I had that coin I would make sure to remove all grease or fat (with acetone or gasoline), then dip it or lay it into a watery solution of potassium sulfide. It takes some experimenting as to how much pot.sulf. and as to how long to expose. By this way a normal chocolate brown color can be obtained in very little time. Rinse and wipe dry. Then I 'd embalm it with olive oil and wipe with a cloth. This, of course does not remove the pits caused by the verdigris however the coin should look nicer. With the coin as shown matters can not be worsened very much anyway. Regards, Sigi

Thanks everyone! Very interesting. As you can tell I know nothing about dipping copper coins into acid, but now I can see the results

I also know nothing about electrolysis except that everyone says don't try it on copper. Would electrolysis give copper coins a similar shiny pitted/grainy appearance?

Steve

Hi Steve, electrolysis is somewhat more difficult than just dipping, I have no experience with it. But there is an excellent book on how they proceed in the British Museum (including electrolysis): James Harold Plenderleith, THE CONSERVATION OF ANTIQUITIES AND WORKS OF ART. The book is still available ($25) but can probably also be consulted in libraries. Regards, Sigi

Thanks Sigi.

If anyone has an image of a copper-coin (preferably not Russian) after electrolysis, could they post it? It may be ugly, but enquiring minds want to know.

I think the coins in question were corroded to begin with, then 'whizzed'. I suggest this because I bought some uncleaned Byzantine coins on ebay a couple of years ago. One was so bad you could barely tell it had ben a coin. This being so, I went to work with my handy,dandy Dremel and a small steel brush attachment.The result looked like what I see in those pics. I have a small electrolysis rig here(never used it on coins though) I'll see if I can find some old copper culls and zap them for you guys.

Thanks! Would be interested in seeing the results.

Steve