If this is Bronze Disease, I'll cry

[Ardatirion]

Oh say it ain't so. I had really high hopes for this coin, you could tell there was superb detail beneath the dirt on it. Today I took it out of its 4 day distilled water soak and used the dental pick on it, the dirt literally flew off to reveal a pretty good reverse, part of a head and this blue.... stuff. What do I do?

[slokind]

It is hard to tell from a photo, but if the color is accurate, as it appears on my monitor, it is too blue to be bronze disease.  The real first test is to take a wooden toothpick, and if the green is powdery and comes off on the toothpick without effort then it is likely to be bronze disease.  Pat L.

[Ardatirion]

The green and blue parts were unaffected by the tooth pick, so I guess its not BD. How should I go about cleaning this? And should I attempt to preserve the blue or the green thats by the head?


PS - I realize this is in the wrong section, could a moderator transfor it to the Uncleaned Coins section?

[awl]

I would clean it because it is not the patina. The patina is the green stuff. A brash brush should clean it up nicely.

-Adam

[bruce61813]

Treat it as if it is Bronze Disease, it does look it. The treatment on't hurt if it isn't, and if it is, you will save the coin.

Bruce

[awl]

Heat can be used to temporarily neutralize bronze disease by removing the moisture that is required for this reaction to occur. Place your coins on a cookie sheet covered with foil. Place in oven at 200-250 degrees for approximately 15 minutes minutes to an hour. This is not a permanent cure since once the coin cools down, the moisture in the air may start the reaction again. At best, heating a coin will temporarily stop or slow the advance of the disease.

It is important to note that the heat may also change the color of the patina. Heated coins tend to be darker after a treatment.

For mild cases, you may want to try a distilled water procedure listed earlier. This may seem to be counter-productive since moisture is needed to start the reaction in the first place, but it does work. (Do NOT use tap water. The minerals and salts in tap water could actually increase your bronze disease.) Over time, distilled water will attract the chloride ions (bronze disease) and gradually remove them from the coin. As the water becomes dirty with chloride ions, change the water often.

You should change the water every few days to a week. You will want to check the coin when dry when you think it may be finished. Repeat as necessary.

DO NOT mechanically remove the disease like a surgeon! It will just make it worse.

-Adam 

[Mark Farrell]

Let me suggest a couple of slight mods to Adams good suggestions.

It is sometimes advisable to remove as much of the blue-green powder as possible via picking with a very sharp needle. This is not really needed if the BD is primarily on the surface, but I would suggest it in the case of pitting. If you don't you will be treating the BD quite literally for months.

I personally don't use DW for treating bronze disease. It can work, albeit very, very slowly.  I personally use sodium sesquicarbonate for BD treatment (or more simply, use Gringott's number 1) which you can mix up with various proportions of baking soda and washing soda, but why bother when Gringott's has it covered anyway.

There used to be a really good article on Bronze Disease by Bruce Nesset under Resources, but it seems like the link is broken.

Finally, treat BD as though it were a viral infection and is contagious. This means that if you pick at it with a needle, wash the tool thoroughly afterward. Clean up around the surface where you picked the stuff out. And do NOT store it with other bronze coins. I know that BD is simply chemical, but it can spread -- I've personally seen this happen to some coins of mine.

Hope this helps,

Mark

[bruce61813]

    If the green was under the brown, then there is a very high probability of it being bronze disease.  It has a tendency to run along under layers along the surface of the flan.
 
    Also, BD is not always just green and fuzzy, if left along it continues to grow and looks a lot like cauliflower with a blue-green color, so I would not take the chance.

  If the link is broken here on Forum, try this http://www.gringgottscoins.com/wst_page2.html , it has the article. FYI Gringgotts #1 has some added chemistry beyond the sesquicarbonate.

Bruce

[Ardatirion]

I'm seriously starting to doubt that this is BD. The DW soak is already starting to push back the blue parts. Plus, I just chipped off some of the blue with light picking - it looks like theres smooth brown metal beneath. I think that the green is a thin layer of oxidation that is removed with the blue. (it only occurs on places on the coin were the blue/dirt was not present)

After I get it a little cleaner by conventional methods, I'll re-evaluate it.

[Ardatirion]

So, I took the brass brush to the blue stuff, i think that's just what it needed. Here's some pics.

Constantine I, 306-337 AD
AE3, 17mm
Thessalonica, 336-337 AD
rosette-diademed, draped & cuirassed bust right
CONSTANTINVS MAX AVG
two soldiers standing front, heads turned inward at one standard between them, each holding a spear
GLORIA EXERCITVS
RIC VII 222
SMTSA in ex.

[awl]

Great job! The coin looks 200% better. 

-Adam

[Ardatirion]

Well, I'm gonna flip this one for now. I don't really have any tools, like a diamond dental pick, fine enough to get at the tiny remaining blue spots and, from what I can tell, the only thing to be done about the red stuff is to grind it down. Still, I'm very pleased with it and may work on it again in the future.