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Cleaning Follies

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ancientcoinguy's Avatar
United States
842 Posts
 Posted 03/07/2011  7:04 pm Show Profile   Bookmark this topic Add ancientcoinguy to your friends list Get a Link to this Message Number of Subscribers
I recently received a shipment of uncleaned Roman coins from an excavator in Europe. One of the smaller ones seemed to have a lot of detail on it, so I chose it first. I began the routine cleaning...warm water, soft brush, etc. To my horror, the beautiful jade-like patina on the obverse flaked almost completely off with hardly any effort exerted on the coin. Strangely, the reverse suffered no damage. Is this normal?

P.S. The coin turned out being an Arcadius AE4 from Constantinople.
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sel_69l's Avatar
Australia
21788 Posts
 Posted 03/08/2011  08:53 am  Show Profile   Bookmark this reply Add sel_69l to your friends list Get a Link to this Reply
No, that would be unusual. I guess that before the coin was dug up, the micro environment on one side of the coin was different from the other. Perhaps one side only was exposed to air or mineralised water from the surrounding soil.

I tried to gently heat a small bronze of Constantius 11 to remove encrustation. It just crumbled to a heap of black particles. I did not loose much value, the coin was only in poor condition in the first place.

Immersing in olive oil for many months is often the safest way to go.
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SPQR's Avatar
United States
327 Posts
 Posted 03/08/2011  09:49 am  Show Profile   Bookmark this reply Add SPQR to your friends list Get a Link to this Reply
Sometimes the exposure to air after being buried for centuries will have strange effects on them. You'll see everything from patina falling off, like yours, to concrete like encrustation that defies everything short of a jackhammer.

I've had good luck with boiling them with washing soda and then a long soak in distilled water. It's still hard work, but it's worth it to see something nobody else has seen for a thousand years or more. In this case, Arcadius ruled until 408CE so your coin is over 1500 years old, which just blows my mind to hold something man-made that old.
Yes, it's a geek thing.
Edited by SPQR
03/08/2011 09:55 am
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ancientcoinguy's Avatar
United States
842 Posts
 Posted 03/08/2011  11:54 am  Show Profile   Bookmark this reply Add ancientcoinguy to your friends list Get a Link to this Reply
Thanks for the tips, guys.
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