BRONZE DISEASE

 

I'm going to demonstrate some of the techniques for removing Bronze Disease. BD is a light colored "fungus", sometimes in shades of blue or green, that will "eat" bronze, leaving unsightly pits- or a pile of crumbs if not treated.

I bought some cleaned/low grade/culls from ebay. I expected that the patina was stripped from the photos, and many of the coins were truly culls; what I didn't expect was that the coins would be infested with BD. Beleive it or not, I haven't had any outbreaks of BD recently, even after all of my experiments.

I believe that the coins were cleaned using electrolysis with salt; but the seller wouldn't tell me exactly how- it's a family secret. Anyways, these show a good reason not to remove the patina of coins. Of the approximately 100 coins, I would guess 30 are showing BD presently. As far as I'm concerned, all the coins are prone to BD, and I'll treat them all.

First up, is the basic washing/basic soda treatment. I scraped the pockets of BD with a paper clip. One can use push pins, needles etc. I recommend something that you can throw away. I believe you can contaminate other coins by using the same instrument. Some people swear that you can't cross-contaminate; but I had a container of coins soaking, one coin had BD, then a week later 10 had BD. Better safe than sorry. I then used a stiff nylon brush to brush much of the BD off. Most recommend a soft brass brush, but I don't want to infect my brass brushes, and the nylon seems to work decently.

Using a mixture of 3 tablespoons washing soda, to 2 tablespoons of baking soda, I mixed it in about one quart of water. I boiled the coins for 15 minutes or so, and let cool. Rinse, air dry, and brush- and repeat. One wants to do this three times.

I then let the coins soak in rubbing alcohol overnight, to seep out the moisture.

Directly below is the scan of the beginning coins, then the coins after the boils, and finally a scan of the coins after sitting for a week or so, to see if the BD comes back.

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After sitting out for two weeks, here's what I have now:

Small amounts have come back, and I'll have to treat them again. I'll probably soak them in a BS/WS mixture for a bit as well.

 

 

TREATMENT TWO

 

Acid-

I'm using Nic-a-lene coin cleaner, which has phospheric acid as the main ingredient. Different acids are supposed to kill the BD, though I've only seen this mentioned and no real proof either way. I'll soak the coins for a couple minutes, rinse well, then let soak in alcohol overnight. Scans below: before, after, after a week sitting.

Phospheric acid doesn't seem to be removing it all, at least on the coin with the huge white pit. I used the paper clip on it to bore it out, then resoaked the coins.Still seems that a bit is remaining.

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The coins have sit out for about 2 weeks. Here's what I have now:

Much of the BD has returned, Phospheric acid is not a way to treat BD.

 

 

 

 

 

 

THIRD EXPERIMENT

Basic soak in 91% rubbing alcohol. I'll nylon brush the coins and let soak overnight.

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After two weeks:

BD was reduced, and no new growth- but not totally obliterated. Alcohol won't solve BD by itself.

 

FOURTH EXPERIMENT

I'll zap these for 15 minutes.