Preventing Bronze Disease?

Thus far, I’ve mostly limited my big purchases to silver. Lately though, I’ve gotten more interested in bronzes and have made a few bigger purchases that I’m waiting on now. I’m a little nervous about the possibility of bronze disease, and wondering how common it is and whether any of you have any standard practices to prevent it?

I store my coins in Saflips in an album, and I know to keep a desiccant with them if I put them in a safe. I’ve seen people mention Verdicare, which sounds like it doesn’t change the look as much as Ren Wax, but I’m leery of putting anything on healthy coins that might have a permanent effect. Is it really necessary to do anything else if I keep them in a dry, controlled environment and only buy healthy coins?

 

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Bronze disease appears as a powdery, flakey light green deposit. If you poke it with a toothpick, and fine light green powder comes off then it is bronze disease. Don't get that powder on other coins or you risk spreading the infection. Hard dark green deposits are not usually bronze disease.

I don't think most people do anything to healthy bronze coins other than store them properly.

Surface bronze disease can sometimes be treated with verdicare. Deep bronze disease that is eating the coin from the inside out can be impossible to stop. There has been much discussion of this topic on the forum if you do some searching.

John

 

Also, your coins are unlikely to suddenly get bronze disease unless they have recently been cleaned and some part of the coin that was protected in the past is now exposed to air and moisture.

Check your bronze coins ever 3-6 months (if you don't look at your coins at least once every six months, what's the point of owning them?) for signs of a green powder that appears seemingly out of nowhere collecting on the surface. Then enjoy your bronzes and sleep well.

 

Thank you for your post, @SeptimusT ! Most of the ancient coins in my collection are bronze and I inspect them frequently. Many of them are NGC slabbed but those that are not I treat with Verdi-Care and store them in archival flips. To date—I've not discovered any with bronze disease but if I do—rather than attempting to treat or "cure" the coin—I'll encase it in Lucite.

 

In MOST cases, bronze disease is easily treatable with, believe it or not, (since moisture is what causes the reaction to begin in the first place) distilled water and a little diligence and patience.

 

air, moisture and chloride. i'm dealing with this on some bronze/copper coins now and presently using BadThad's verdi-care to hopefully seal the coins and arrest the process..bronze disease happens when the bare metal is exposed to the elements. according to sources, removal of any one of the 3 stops continuing damage of BD. there's a few threads on this here on CT.

 

Before:



After:



Bronze disease sucks hard!

My brother worked for a good couple of months cleaning this one up with distilled water, baking soda and washing soda. Finally, he baked it in the oven.

Hopefully, he doesn't get any more bright green spots.

Erin

 

In a word: no.

 

So the general consensus seems to be that you don’t have to do anything, but you can. And if worst comes to worst, there’s still hope. So that’s good. Makes me feel a little less paranoid about moving into new territory. Thanks for your advice!

 

I agree with your assessment.

 

Can I ask, what temperature did he bake it at?

 

My opinion, after discussing the subject with several other collectors of bronzes, is that for the most part as long as you keep your coins dry and don't buy bronzes with existing disease, you are OK. I live in Colorado so keeping them dry is super easy for me but if I lived in the humid Southern state I grew up in I'd make absolutely sure that wherever my coins are kept stays good and dry at all times and if not I'd pack them with plenty of dessicants. Even in dry-as-a-bone Colorado I like to keep dessicants with my coins just for a little more peace of mind while they're away in the bank vault.

 

He baked it at 375 for 45 mins.

Erin

 

Thumbs-up for the hard work!

 

yeah, easily treatable for a few days, then it re-appears

 

I’m so confused with BD. I’ve read elsewhere you do it at 250 for 20 mins

 

I have a question for you. I’ve read a lot elsewhere too that it’s a powdery substance like you describe. However, i think this is misleading. Most of the time when i encounter it, it’s easier to identify by unsightly blobs in relief, usually light blue color that creeps in crevices or is under patina. When i pick at the blob, the surrounding metal is softer than usual and is easier than normal to scrape/slice off with a scalpel. The softer metal tends to be redish brown at the top, darker brown as it mixes seamlessly into the lighter brown metal. I sometimes get impatient and cut it all out, then i’m left with a pothole here and there but i see no other choice. As ive read, it’s irreversible, so i gotta stop its spread i guess. Im kind of new to ancients, haven’t used sodium sesqui-whatever it’s called but i imagine it eats the BD away also, just at a slower pace and with less damage to surrounding metal. I also tend to encounter it a lot when i see the same blue and red colors peeking through patina, and when i take a stab at it, it’s like a soft blue dirt or sand that i push/scrape off to the lighter brown metal. The end result is a coin stripped of patina because underneath is soft, moist, seemingly corrosive blue dirt that i think has to be removed in order to prolong the coin’s life for posterity. I’ve almost had it with bronzes because of this common crud i’m running into, maybe it’s just the ebay stuff ive gotten. But i’ve read some posters say never get rid of patina or show the bright copper color, but my only choice is to leave moist blue dirt on top so it can soften and eat away at the copper over time. I hate it so much. Sorry to write so much, just frustrated

 

What you are describing is corrosion, not bronze disease (BD). They are similar, but not exactly the same. It's sort of like the difference between scars and skin cancer. Scars (forgive me if I'm offending anyone) can be unsightly, but they won't spread. Skin cancer, however, can continue to spread and cause additional damage.

Corrosion is caused by the interaction of the coin with chemicals in its immediate environment, i.e. the ground surrounding it. Once the coin is removed from that environment, the corroding process ceases. But you are still left with a (usually) hard blob on the surface of the coin that is some combination of materials from the coin and materials from the environment. So removing the corrosion removes any of the metal from the coin that has reacted to the chemistry of the environment. Presto: surface pitting. Scars.

BD starts the same way, but there is a critical difference. The nasty chemicals turning your bronze coin into powder remain with the coin even after it has been removed from its recent environment. The only way to stop the reaction is to either neutralize it chemically or leach it out of the coin with distilled water.

I've never baked a coin after treating it for BD, but I can understand why someone might want to. The point is to remove any last traces of moisture within the coin, since it's the moisture--usually in the air--that allows the chemical reactions causing BD to occur. But two points:
1) I would do it at a lower temperature. Seems like there would be less chance of damaging the coin. I've heard of people baking post-treatment coins at 200 degrees Fahrenheit for an hour or so. But that's just my instinct. I have not evidence to back this bias up with.
2) To cure BD you really need to remove all the chemicals (chlorites? chlorides?) that are causing it. Removing all the moisture will stop the reaction--since they need moisture to occur--but it might give you a "false negative". That is, even though you've stopped the reaction, there might still be some reactants left in the coin that you haven't completely gotten rid of. It's possible that under the right conditions, the BD might return.

 

Hard red and blue deposit don't usually indicate bd. Pink crumbly deposits are often what is left behind by the bd action.

Something to remember is that bd is only active when the humidity is over 50%. A coin stored in a dry place can look fine until exposed to more humidity and then you get the bluish green blossoms. Like when someone ships it to you from a dry region.

Coins bought from good sellers are less likely to get bd than random eBay sellers who may be using pool acid to clean their coins. ☹️

Note that there are great eBay sellers and awful ones and feedback means nothing.

John

 

I really appreciate your response, and it's cleared a lot up for me. Thanks! I have a question though. If I find some bluish dirt/stuff on the coin, what would you recommend. I've been trying distilled water for days now, and some of the coins are developing a blue verdigris on different parts of the coins. I started panicking that BD is spreading in the water! I feel compelled to pick away at them. I'm noticing potmarks like you said. Should I only lightly pick at them, bake them/use acentone swab, then finally smother a little with Renwax (I have some)? Thanks