Well, I generally don't like the overall appearance of this cleaned and repatinated coin. It looks very unnatural now - the colour should be dark honey brown, not dull black. In fact, the photograph is too small to determine how this specimen really does look like...
Usually, the cleaning should has a clear purpose: either to enhance the look of the coin or to preserve it (if endangered by active corrosion).
In my opinion the most important thing while cleaning is to know when to stop - rather too early, than to late.
Last year I
had an interesting case. After receiving an attractive "
follis" of
Constantius I decided not to clean it, only to remove some loose yellowish crusts. Doing this I realized, that there were spots of active
bronze disease under the solid looking dark green encrustations! I
had no
choice, but to remove them all... In this process many traces of original, darkened
silvering came to light.
In the end, after conservation, the coin has retained much of its original appearance and beauty. Its colour is mostly dark brown (AE) with darker spots (
silvering) and the surface is slightly glossy (without
smoothing!). At a closer look also some traces of corrosion (little craters on the surface) are visible.
At least I've tried to treat this coin and its
history with as much respect as possible...
A
sestertius doesn't have any
silvering, so: why uniformly black? In its original state of preservation one could see the proper colour under the encrustations well enough!!!
Zenon M.