Just picked this one up in a recent Savoca lot as a quick flipper, but on closer inspection it looks like it could have some promise. It is a Pius / Aurelius Caesar sestertius that I have always had on my want list, well struck and perfectly centered, but the patina is, uh... white? I've soaked bronze coins before, usually without much success, but this one might show promise. So, to the more experienced cleaners out there - is there anything that can be done to darken the coin and bring out the detail better? Maybe a few months to a year in olive oil? Should I give it an acetone or peroxide rinse?
Is it still covered in dirt? It appears so by the way the letters meld into the fields. I would soak it, but after a week or so give it a good scrub with a denture brush and see if some of that comes off. Soaks only work on hard mineral deposits, when a coin is completely covered in dirt it will overload the water.
I would wait until you have the coin in hand. Soak in distilled water, when the water becomes cloudy, change and soak a few more days. Brush with a cut down toothbrush between soaks and see what happens. Coin shows promise, it would be a shame to rush things and risk it.
If you want to go a little beyond water and brushing, olive oil is a safe next step. You could also try some VerdiCare.
Thanks for the replies. I'm not sure how much more brushing can be done on this one; the surface is pretty smooth and I don't get any residue when I rub it or gently scratch with my fingernail. I'll give it a distilled water bath to see if I can get Pius' face cleared up a bit, then I'll probably go for an oil soak. Really hoping this one turns out well!
Funny this thread should come up now - I just got a small lot in the mail today which included this busted Septimius Severus "limes" denarius that is somewhat "white." Not sure it is the same stuff that afflicts the OP, but it looks similar. It seems very fragile to me, so I doubt I'll do anything with it, but I will continue to watch the thread with interest. Septimius Severus Limes Denarius (200-201 A.D.) Rome Mint? [SEVER]VS AVG PAR[T MAX], laureate head right / [PR]OVID AVGG, Providentia standing half-left, holding wand over globe to left and sceptre. RIC 166; RSC 586 (1.90 grams / 18 x 12 mm)
Do not leave it in olive oil for extended periods. Olive oil is slightly acidic. An overnight soak won't hurt anything. But if you leave it in for a week or two you'll notice the olive oil turning bluish. That's copper leaching out of the coin--not good. If you are still not satisfied after a couple of DW soaks and brushing, as described by medoraman and Pishpash, I would escalate. The next level on Glenn's Ever-Increasing Cleaning Harshness pyramid would be soaking followed by brushing with a brass bristle brush, which you can find in most hardware or department stores. Still not satisfied? Escalate to brass tools (buy a brass rod from a hobby shop and file the end into a point) and a stereo microscope. Worst case scenario is advancing to electrolysis, the top of the pyramid, which will remove everything on the surface, including the patina. My suspicion, though, is that removing the patina will reveal a lot of surface roughness. You might not want to go there.
