This is a coin from
Neapolis (in
Campania) which
had a dark green
patina over more than half of its surface. It's not the most wonderful specimen, but it could be worse. When it arrived it
had green eruptions in several places, similar to
bronze disease but not showing any propensity to give off light green powder, so if bd, then not active. One spot looked lighter and more powdery, though (bottom left of the
lyre), so I decided to give it the usual treatment: simmer for an hour in sodium sesquicarbonate solution.
The result was that all the dark green
patina turned light blue .. this really
reduced its
eye appeal, but there's not much I can do about that now. The
area without that
patina hasn't changed much, but now it stands out in contrast rather than blending in. I tried a cautious dip into vinegar on the principle that acidic compounds are
red, alkaline ones are blue; the only result was to clean
part of one edge so that the original bronze shone through. (Bottom right of the
reverse.) So I will not try anything else.
So, a note of caution for anyone looking to treat coins with this
type of
patina. Balkan
patina doesn't mind this treatment one
bit, but
Italian does!
It does look as though some areas of corrosion have been cleaned out, so I
think the treatment was necessary. But
had I known what would happen, I would have chanced leaving it alone to see if was stable.
Coin
Type: A bronze
AE20 of
Neapolis in
Campania, c. 250-225 BCE. 18mm x 20mm, 6.41g.
Obverse: Laureate
head of
Apollo left; Π behind.
Reverse:
Kithara leaning on
Omphalos,
bucranium above. NEOΠOΛIT(ΩN) below.
Ref:
Sear GCV 558
var;
SNG ANS 531
var.