Last week began with my hasty purchase of a "Gordian III" sestertius.
This week is ending with a long term conservation effort on a Macrinus sestertius.
Now that's what I call progress !
When "Gordian" arrived I noticed (as I had suspected) that the coin had some sort of lacquer applied to it and needed a good bath in acetone to remove the shiny (water resistant) surface. After which I rubbed the brown surfaces with a sharp bamboo skewer. A small area at the throat crumbled under pressure but the underlying material was black and did not appear to represent any sort of serious corrosion.
So to recap .....
Our "Gordian III" after acetone bath
And our "Gordian III" miraculously revealed as a sestertius of that pesky praetorian Macrinus
Most of the brown fossilized fecal matter has come away with relative ease. Distilled water and frequent brushing. A few 'pimples' were popped using a tiny blade as a scraper. The patination seems to have three layers
Brown which resembles fossilized sheep dung
(removes steadily if not easily)
Olive green/black which is rather rough and "pimpled"
I love the color but not the surface
lastly a dark black layer which seems to have a pleasingly smooth surface.
I assume it to be bronze below this but have not penetrated it (hopefully I won't either)
On the reverse at 1 o'clock a small chip in the upper layers revealed the black layer. I used the blade (90 degrees) to gently expand the area.
Another 'chip' below the P in PVBLICA shows an area expanded slight during (frequent) brushing.
I plan on soaking the coin for another few days to remove what is left of the brown material (excepting the edges) but I wonder if another approach would work better on the hard green layer below ?
I would love to have the coin be green but alas it seems a superior smooth layer lies below it. I don't want to strip it to bare metal but what would be the best technique on this hard green pimpled layer ?
Olive oil ?
I remember seeing some rather incredible conservation jobs done by some of our CCF experts. But that was a few years ago and I can't even remember who it was.
Opinions ?
I forgot to weigh him in on arrival but at last check Macrinus still weighed a healthy 26.23 grams
Posted 09/28/2017 8:51 pm
