A case of bronze disease?

[roger_malvin]

I recently finished cleaning and attributing this provincial 20mm (I believe it’s a Perinthus bronze with a Dionysus obverse and Heracles leaning on club reverse).  I was about to flip it and take some small satisfaction in finally finishing my first coin (it only took me 11 years – the period of time from when I first bought a batch of uncleaneds to when I finally took the time to figure out how to clean them).  But then I became worried that the green areas on the coin that I originally took for copper oxide could in fact be spots of bronze disease.  I am particularly worried about the small spot on the obverse in the tail of the hair at 9 o’clock, and the area of the outer rim on the reverse (especially at 12, 4, and 8 o’clock).  Right now nothing is powdery or dust-like, but I just want to make sure that I am not ignoring something that should be treated.

I know that this question gets asked a lot, and the answer is probably painfully obvious to many, but any advice to a novice eye would be greatly appreciated.

Thanks, Kentston

[Arminius]

From what i can see i agree - bronze disease.

This red copper oxide surface is expecially endangered an a good basis for BD attack.

Boil the coin in soda solution (if possible: chlorine free water), rinse with distilled water, dry and brush off the green powder.

Observe the dry coin and repeat this procedure as often as necessary. (Sometimes, if the green spots return even after many cyles, they have to be scatched out by a scalpel down to the metal.)

regards

[roger_malvin]

It's as I feared.  I just hope that there has been no transfer to other coins in my careless handling of this one.

Thanks so much for your reply.  I will begin treatment with Gringott's #1 this weekend.

Kentston

[roger_malvin]

I have one follow up question. Unfortunately In my zeal to finish the coin, I already have waxed it.  Would boiling the coin in Gringott’s #1 remove the Ren Wax?  Or would I have to employ a different tactic?  For instance, I’ve read that acetone will work, though I must admit I am a bit leery of applying such a strong chemical to an ancient coin...

Thanks, Kentston

[Arminius]

First of all: I have no experience with Gringotts at all.

Boiling in water solutions, especially with detergents, usually removes most oils, greases, waxes and associated dirt. Acetone soaks at ambient temperature (low boiling point !) even faster.

Acetone is no strong chemical, especially not concerning coins and patina. It will not change any metal or natural patina. It may change the colour of the patina if this is greased. By acetone the patina reversibly becomes brighter.
But Acetone and it´s vapours may burn! So be careful with fire and sparks.

[Mayadigger]

Ave!

Sorry all, but I see zero BD.

Just a stripped coin that, at this point, needs conservation/restoration,

Best,

Kevin

[roger_malvin]

Acetone is no strong chemical, especially not concerning coins and patina. It will not change any metal or natural patina.

Sorry about that.  That’s the non-chemist in me that crudely equates strong chemical smell to strong corrosive power.  Perhaps too acetone’s use as a paint thinner caused me to think twice about what it would do to patina (though I do realize that 1) this particular coin doesn’t really have a patina; and 2) patina is not paint.  Or rather, it shouldn’t be...)

As to whether it was BD or not, I’m not exactly sure, though I am leaning towards a tentative yes, if I am reading the coin’s reaction to Gringgott’s #1 correctly.  After the initial boil and soak, the previously green spots on the coin turned a dark brown/black.  Lightly scrubbing with a toothbrush then removed most of them.  After 72 hours of further treatment, the green is pretty much completely gone.  I have posted pictures below of how the coin currently looks, which, admittedly, is now worse for the wear.  I was going to let it air dry for five or so days and see if any of the green returns, and then, well, that leads me to my next question.

Perhaps I was a little cavalier in throwing out the term “cleaning” to describe my handling of the coin.  If I recall correctly, the coin pretty much came to me in this stripped/zapped state, so there was little that I actually did to it other than soak it for a decade in olive oil.  It wasn’t until I returned to these coins a couple of months ago that I realized that there was no more cleaning that could be done to it. 

But I must say I am rather fond of this coin and am curious as to my best options of conserving it, especially since I am now even less pleased with its appearance that I was earlier.  Should I leave it as is, or consider some other means of conserving/restoring it?  And I realize that opinions will probably vary greatly.

Thanks in advance,  Kentston

[Joe Sermarini]

Do not wax it.  If you wax, it will not re-tone and it needs to re-tone. 

You could speed up the toning by using dellers or liver of sulphur, and then wax. 

You could also burnish it (smooth it with jewelers burnishing tool) and then darken and wax.  In my opinion, that is more harm than good.  It certainly is NOT conservation or restoration.  It is further damaging a damaged coin to make it appear more attractive.   

[roger_malvin]

Thanks, everyone, for your advice (and I see that this has spawned a poll about conservation/restoration).  I’m not yet sure where I stand on the purist scale -- perhaps 85% purist right now? -- though this could change some as I continue to learn and encounter more problem coins.  Right now, though, I think I will take a more conservative approach to finishing this coin. 

The coin’s currently back in BD treatment, as I recently noticed that there was some powdery blue stuff still lurking in a few deep recesses along the side of the coin.  When this is done, I don't think that I will try and smooth it, but I will use some Deller’s to help retone it.  For sake of completeness, I will post some pics when done.

Thanks again, Kentston