A Question about Caring for a French Plaquette

[milesofwho]

I recently acquired this French plaquette, and noticed it has some green spots. What is the best way to treat them, and make sure that they do not spread?

[robinjojo]

That's a beautiful plaquette. 

It's hard for me to see the green spots in the photos.  Are they hard or soft and powdery?  This can be determined with a wooden toothpick.  A powdery spot will come off on the toothpick while a hard one won't.  

A powdery spot is likely active corrosion, while a hard one is benign, but also hard to remove and best left alone.  Active corrosion needs to be neutralized; otherwise it will continue to spread.  

The plaquette has a really nice patina that should not be disrupted if possible.  Distilled water is used in the case of active corrosion, but treatment should be limited to the spot or spots rather than immersing the entire plaquette in distilled water.  Using a wooden toothpick and a cotton swab, soak the swab in distilled water and apply it to a spot.  After a few seconds see if the spot comes off with the toothpick using very gentle action.  Dry immediately with a piece of paper towel.  There still might be some traces and you can try the same approach again or leave well enough alone.

That said, I would take a very slow, cautious approach with this object.  Bronze is very reactive to environmental conditions, especially humidity.  If you live in an area that experiences frequent high humidity, try storing the object in a dry place, with some silicon packets.  See if this storage stops the spread of the spots, keeping in mind that bronze will naturally change color over time.

[Hrefn]

Try pasteurization?

[Al Kowsky]

The medal won't look any worse for the duration of your lifetime, so leave it alone 😉.

[milesofwho]

The green spots are hard, so I will happily leave it be. I should have prefaced that the green spots were there since I purchased it about six months ago, and I have noticed no change since then.

Edited June 28, 2023 by milesofwho

[thenickelguy]

Nice plaquette.

I don't see any real issues, It isn't perfect and like new but there's nothing worth risking irreversible problems. I am like you, little imperfections drive me a bit crazy. That's me, most people can live with minor issues on medals over 100 years old. I agree with Al Kowsky, this won't get any worse in our lifetime. if you keep it in a safe dry environment.

It is probably verdigris, which has already altered the surface in color underneath if you were to remove it. There might be some microscopic pitting if somehow you could just remove the green. 

I just don't see a problem. best to protect it from heat, dampness and focus on the whole bronze rather that the minuscule imperfections.. But I know how it can be bothersome. I'm OCD. Easy for me to say, not so easy for me to do. The responses will be a survey, most of us aren't going to be bothered about less than perfect when it is someone else's treasure. We like it just the way it is.

[Paddy54]

Unless the plaque has a coating of sort like varinish...I use Acetone and Verdi care on most  all medals , esspecially those of copper,  bronze,  and N/C . The acetone will clean ,and the verdi care stop any rot . I trust both unless again you supect a coating of sorts tjat you are uncertain about the chemical composition.