Numismatic and History Discussion Forums > Uncleaned Ancient Coin Discussion Forum

Bronze Disease

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Virgil H:
I have a coin with bronze disease (my first one as far as I know) and just read the Numsiwiki article on treating it with Sodium Sesquicarbonate. Looking at forum search results, I thought there was more specifics on this, but I didn't really find that. Is this still the preferred method? I have a couple of questions.

I found two methods for curing bronze disease. One uses what I mentioned above. The other involves sodium bicarbonate and sodium carbonate and involves boiling. Is one of these better than the other? Is there a newer and better way?

The other thing is how do you know when it is cured? I worry about putting the coin back in my trays and having it come back in a month or something along those lines. Also, is BD contagious? It seems that it is from one of the Numiswiki articles. This coin has never made it into my trays and has been sitting on my coffee table for a few weeks in its flip. My coins don't go into my trays until they are photographed and I am lucky in this case I haven't done any photography in a while. This has been developing over this period, I think there was a small green spot I wasn't worried about when I was doing attribution, but today I noticed it has spread and much of it wipes off, so I assume it is BD.

Virgil

v-drome:
When I have a coin with only small isolated spots of BD, I usually try to physically scrape it out down to solid metal before I resort to any chemical means which might remove the patina on the rest of the coin (that is, if there is a patina worth saving).  I will then put some mineral oil in the hole to try to seal out any more corrosion.  Then I keep an eye on it to see if it returns.  I don't know if this method would have the approval of experts.  I would also be happy to hear any other opinions.

I found this fairly concise article of interest:
https://www.brown.edu/Departments/Joukowsky_Institute/courses/greekpast/4867.html

SC:
I also think it is best to start with small steps.

Clean the BD out fully.  I then bake the coin in the oven to drive out moisture.  Also sitting in the sunlight helps ensure no moisture.

I then leave it for observation to see if anything returns before trying any chemical fix.

This will work on some but not all.

SC

Virgil H:
Thanks v-drome and SC,  I will try the non-chemical method first and see how that works.

Virgil

Joe Sermarini:
I am repeating myself but... 

Many times what looks like bronze disease is not really bronze disease. Over time, I collected a group of coins that I thought had bronze disease and set them aside. They all had deep pits with light green inside. Somehow they ended up lost in my garage, which had no climate control at that time. Five years later I found the coins, not one of them had changed. None of them actually had bronze disease.

On the other hand, I have had perfectly normal looking coins develop bronze disease and a portion turn into green dust rather quickly.

The first thing to do is observe. Bronze disease shows changes quickly, often in days or weeks. No changes, no worries.

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