Patina

murphy · Senior Member

Rhubarb brought up the question of what is patina in another thread. I'm wondering how patina might affect the collectability of Indian Head cents that I dig up out of the ground after locating them with my metal detector. I then clean them in Mineral Oil. If I soak them for a day or two then rub them with a cotton cloth I notice that the all-green surface corrosion turns to a pleasing brownish green patina. I might have to soak/rub several times if the cent is really green. But if I over-do it then the cent becomes all brown and the corrosion disappears and that leaves a very ugly pitted surface. SO, I can't be too liberal with this cleaning process. The best I can hope for is to achieve a greenish-brown color and still maintain a smooth surface.

How would their greenish-brown patina they get after cleaning effect the value of an IH cent?

eagames · Expert Member

Probably the value is better when you stop at the point you described because if it becomes pitted then it's porouse and that lowers the value even more. A collector might not mind a coin that looks a bit greenish but still has nice details more than a porouse coin. Still if the collector truly wants no problem high grade coins they probably would pass on anything we dig.

BTW I do a lot of detecting too, I'm always kidding the other detector folks when they dig a realy old looking corroded cent I yell out modern zinc!!! Then they find some nice looking brown XF it turns out to be a copper memorial or a wheat Laughing

I have heard that one reason a coin will never re-tone the same as uncleaned is that on it's original surface are impurities and they change the way the original patina grows. So a cleaned coin will not have the impurities and will re-tone in a different way. On top of that on high grade coins people will see that they are missing the flow lines.

Bob P · Site Admin

Murph,
The patina can make or break a nice coin. I agree with Ed in that you should stop before you get to the point where the pitting shows. A pleasing brownish-green color can be very attractive on an IHC.
Ed...I read with interest about the theory on why coins won't re-tone. Here's a little experiment to try. Get two brand new coins. Put one in a flip or something, and the other on a window sill where it gets some sun on it.
Take two more new coins and dip them in a cleaning solution like TarnX or a copper cleaning liquid. Blot them dry, and do the same thing. Put one in a flip, and the other on the window sill. Compare them over a few weeks and see what happens. Let us know what happens.

eagames · Expert Member

I had a few indian cents that were brutaly cleaned with an eraser or something. They looked awful and I tried many things to make them look brown again since they were ruined.

The one thing that did work was get a blob of soft sticky mud. Stick each coin in a cookie size ball and bake them in the oven. After 30 minutes I opened one and it was getting brown, I got them wet again and put em back for another 15 mins and after a few times doing that (getting the cookies wet and putting back) the coins inside were a pleasing brown color. The mud needs to be from under a plant so it's sticky.

I'm sure graders might notice it was not original but they looked much better than they started.

carlb · Advanced Member