I recently got this Magnentius
which while not an uncleaned coin, needed some fixing up. The "patina
" was a mixture of ancient grease, dirt, and tarnish which, while soft, is impossible to remove manually without scratching
up the coin - it is like a slippery ugly black varnish. I forgot to photo the coin before I began but the seller photo's show the look of the coin before cleaning. The obverse
is particularly bad because it is lightly struck.
After some scratching
at it with hard tools
I decided to let it soak in some WD-40 oil for a few hours and then work
at it with a cotton Q-tip. The combination of light scraping, soaking in oil and rubbing with fabric
basically removed this sludgey coating. Since WD-40 is volatile (and not cheap
) I sprayed just enough to cover the coin in a porcelain screw-cap container.
The final result is shown. The little brownish spots are what is left of the coating. My guess is that this stuff is ancient in origin -possibly the remains of grease that was put on the coin to help
preserve it when it was put in the ground. The oil-base makes WD-40 reasonably effective at removing it without a lot of work
There is of course some sacrifice when this stuff is removed but fortunately the metal underneath is in pretty good
condition and the coin, in hand, is much more presentable.