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Author Topic: bronze disease in distilled water? or something else  (Read 745 times)

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Offline Blayne W

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bronze disease in distilled water? or something else
« on: March 09, 2021, 11:36:54 pm »
I was wondering if bronze disease can start in distilled water?  I have several coins that I had soaking in distilled water for several months and checking on them today it looks like some may have developed bronze disease in the water.  Is that possible?  I snapped a few pictures which are attached.  It basically looks like I have a white powdery substance in the water, doesn't really look the bright green though.  I poked at it with a toothpick and it sure crumbled, so am assuming bronze disease.  I thought distilled water was ok for long-term soaks so I guess just want verification that this can happen or maybe it's something else leeching from the coin??   I am not a chemistry expert so this baffles me.

Thanks for any help.

Offline v-drome

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Re: bronze disease in distilled water? or something else
« Reply #1 on: March 10, 2021, 01:41:13 am »
Hi, Blayne.  I have had white spots like that on some of my coins.  It is not bronze disease (copper chloride) but something similar, maybe involving lead?  Since ancient coins have any number of different metals in the alloy, if they have crystallized into separate elements then any moisture can enable what is known as dissimilar metal corrosion.  I'm not sure of the exact type of corrosion you have, but if you can remove the corrosion by-product mechanically and keep the coin dry it should prevent it from spreading.  Other members may have more information.  I have occasionally used a tiny amount of mineral oil in the pits left over from the corrosion to try to keep moisture from reentering the surface of the coin, and this seems to help.  Let us know how it goes.

Jimi

Offline SC

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    • A Handbook of Late Roman Bronze Coin Types 324-395.
Re: bronze disease in distilled water? or something else
« Reply #2 on: March 11, 2021, 08:48:33 pm »
In seawater yes, but shouldn't start in tap water or DW.

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Offline Ron C2

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Re: bronze disease in distilled water? or something else
« Reply #3 on: March 11, 2021, 10:01:08 pm »
In my opinion, you have minerals leaching off the encrustations, and likely not hte base metal of the coins.  I don't think there are any bronze-oxides that are white. 

In terms of DW soaks, DW is only effective because it causes ion migration from mineralized objects (like dirty coins) to the de-inonized fluid (the DW), thereby loosening crusties.  DW should be changed daily, even when soaking for months, or it loses effectiveness. 

It's possible the white stuff is also bacterial growth from leaving dirty water sitting for months... just saying.
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