HELP! Verdigris / Bronze Disease Destroying My Ancients!!

[Alex M4]

Hi folks,

I have been collecting ancient coins for roughly 5 years. My collection is primarily Byzantine and Late Roman bronze folleis, with a few silver and gold mixed in for good measure. I recently began to notice the dreaded, horrifying verdigris/bronze disease appearing on a large number of my coins. It sometimes appears as neon green dots on surfaces, and other times like a fuzzy blue-green coating.

I need help to remedy this problem now before it spreads and annihilates my entire collection!

They are stored in a Beba chest of 10 drawers in a cabinet with a door. I have placed weather stripping all around the crevices/openings of the cabinet and this has brought down the humidity to ~40%. I live in an extremely humid climate in an older home which has difficulty managing the overall humidity--so 40% is much lower than if they were stored elsewhere in the home. Silica packets strewn throughout the cabinet and a dehumidifier have not been able to bring the relative humidity lower than 40%.

I have read extensively and some sites suggest a complicated chemical process to remove verdigris using BTA (C⁶H⁵N³). This is not really an option for me. On the other hand, I've seen that some people do olive oil soaks, which may work, but can also damage the patina of coins; some of them have nice sand patinas or very fine surfaces. Some also use acetone--has this worked for anyone? I know that there are also some products available on the market, but the one product designed to remove verdigris seems to be out of stock worldwide with no more supply being produced.

I truly appreciate any help you might be able to provide. It's devastating to see my collection of coins that have survived centuries being degraded before my very eyes.

Thank you!

[JBF]

Acetone is used to clean PVC gunk off of coins, I think you can do the same thing with alcohol.  Polyvinyl chloride reacts with water in the air, and forms HCL (at least as far as I understand the chemistry.  Even if you changed flips, many dealers use PVC flips and so there can be PVC gunk on coins.

The idea at least for purified water, is for stuff to react with the water after a long soak instead of your coins.

You probably got two problems, the environment you have them in (you want an inert environment), and the disease on coins that have already started.  Mahogany or other fruit hardwoods are best, Oak is particularly bad.

Again, I am not a chemist.

You might get a dehumidifier and some dessicant

[Robert_Brenchley]

Can you keep them in an airtight container with dessicant? You also need to treat the affected coins, of course.