Bronze Disease

[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.

[Virgil H]

It really doesn't matter, but this post shouldn't have been moved. This is not an uncleaned coin and I think it belongs under conservation, which is what I am trying to do with it.

That said, Joe, this one is changing, it is the first coin I have had that this seems to really be BD. I wipe off the dust and it comes back fairly quickly. I do have coins with green spots that are stable. This one I am not so sure about. Maybe I will post a photo. Thanks for all the responses.

Virgil

[SC]

Interesting question about where does the discussion on bronze disease go. 

I always assumed it went under uncleaned (that is why I moved this thread there) and that the conservation section of Photography, conservation and storage was more about ren-wax, etc.

So, I did a search on BD messages - out of the first 100 to come up 30 were in Photography and conservation, 39 in in Uncleaned, and several important messages were in places like Beginner or Roman (also lots were just references to the fact a coin had BD in Identification etc. threads).

This seems to indicate that we have a bit of a problem as the BD discussion is split in at least two places.

I still think that there is more discussion, especially about treatment methods, in the Uncleaned.

But perhaps we should decide once and for all and maybe then move all the relevant BD threads to the chosen section...

SC

[Virgil H]

I agree with you. In a couple of scientific articles I found online, the topic was clearly in what I would call conservation as the discussion was about dealing with how to prevent it in the first place, storage conditions, and trying to keep it from coming back once treated. For example, in a museum, it can be more difficult to maintain humidity in a display for public viewing versus in a vault. And, the discussions went far beyond coins and discusses larger artifacts, etc. I need to redo my search, what I was finding wasn't helpful and I know I have seen lots of discussion over the years on the topic. I actually have a couple separate questions that are related to this discussion, but are much wider in scope. I will probably put the question about storage in the Conservation section. I also have a question about Ron Wax I will post if I can't find what I need in a search.

Thanks Shawn.

Virgil

[Josiah Y]

Can't BD be treated with distilled water soaks... its the slowest but least intrusive method. You mechanically clean off all signs of it and do regular water changes... a powder substance will form in the water around the coin but will gradually make less and less as time goes on. Eventually the water will remain the same... and the BD is gone.

[v-drome]

Bronze disease is caused by the reaction of water and oxygen with impurities (chlorides) in the metal and patina of the coin.  So no, soaking in water will not stop it, and would probably make it worse.

[Aarmale]

Bronze disease is caused by the reaction of water and oxygen with impurities (chlorides) in the metal and patina of the coin.  So no, soaking in water will not stop it, and would probably make it worse.

Distilled water, free of chlorides, can be used to gently remove BD in some cases. The BD cannot grow easily in distilled water since it deprives the coin of available oxygen, while softening the BD and neutralizing some of the acid.

A nice set of slides that I refer is by Sanchez and Harl: http://www.crescentcitycoinclub.org/seminars_and_programs/Bronze%20Disease.pdf

[v-drome]

Hi Aarmale.  I see your point with bronze, but I still believe the water activates the reaction.  I think some bronze coins will just be very susceptible to bronze disease because they contain impurities including chlorides in the crystalline matrix of the alloy. 

Best regards, Jimi

[Josiah Y]

A nice set of slides that I refer is by Sanchez and Harl: http://www.crescentcitycoinclub.org/seminars_and_programs/Bronze%20Disease.pdf

LOL that slide deck says Renaissance Wax "makes the coin worthless to a collector, very difficult to ever clean again, and it's very hard to remove"... wow wrong on all 3 points.

Not sure why people say its hard to remove, just boil the coin for a few minutes and it'll come right off or bake the coin in the oven at 150 on top of a paper towel and it runs right off. I've it certainly doesn't make the coin difficult to clean again even if you don't remove it. I don't sell the coins i clean but i don't see how it'd ruin the value. It it does then that'd be a nice way to make some money... buy a "ruined' coin and remove the wax then sell the coin at its restored value.

[Nathaniel N2]

A nice set of slides that I refer is by Sanchez and Harl: http://www.crescentcitycoinclub.org/seminars_and_programs/Bronze%20Disease.pdf

LOL that slide deck says Renaissance Wax "makes the coin worthless to a collector, very difficult to ever clean again, and it's very hard to remove"... wow wrong on all 3 points.

I am now accepting any worthless waxed coins. I'll even pay for shipping.

Great guide. Got to treat bronze disease right.