Got this beautiful coin on last week (https://en.numista.com/catalogue/pieces9741.html) but while it's well preserved on one side it's almost all green on the other side (but you can see a well preserved coat of arms beneath that green crust).
(Photos got rotated on upload. Quality is not great, but it's just to show the damage extent)
What can I do to remove the verdigris without damaging the coin? (it's not a low value coin)
If you go here and search "verdigris" you get so many awesome threads on this. I was going to post some for you but there really are too many for me to start listing here.
In particular you want to have a look at anything Fluke has written on the topic. He's a wizard when it comes to this stuff.
Quote: "MonaSeaclaid"https://en.numista.com/search.php?cat=Forum
If you go here and search "verdigris" you get so many awesome threads on this. I was going to post some for you but there really are too many for me to start listing here.
In particular you want to have a look at anything Fluke has written on the topic. He's a wizard when it comes to this stuff.
Here's one thread featuring his work: https://en.numista.com/forum/topic41034.html but there are many more as well.
Good luck, let us know what happens.
Yeah, I searched the forum, but I'm asking the safest method before trying anything drastic.
(Hot water and toothbrush did anything but reveal the full extent of the verdigris)
Firing looks like the best method (but where will I get a blow torch here?). What materials are easier to get, the ones for firing or the ones for electrolysis?
I'm a complete novice on this matter, it's my first coin needing this.
I'm sorry, I'm not experienced enough to help with that part.
I think it's fairly individual which materials are easier to obtain. I suggest you change your title to include "verdigris" or some other words to catch the right people. Just to say "copper coin" is so vague.
Keep in mind that I am not as experienced as most in these forums, but I picked up a Roman Follis for less than $5 when I first started collecting. It was basically green when I got it.
I had a couple of packs of WetOnes brand antibacterial hand wipes on hand. Not knowing any better, I gently wiped it clean with a couple of those wipes. Rinsed it with purified water and gently dried it. The green was gone.
That was almost 3 years ago now, and the coin looks the same as it did after I wiped it clean.
I then read that I should never, ever clean a coin. Oops... We live and learn.
I don't know the value of the coin in your picture. So, I am not recommending it, but I thought I would share in case you found it helpful.
Quote: "MonaSeaclaid"I suggest you change your title to include "verdigris" or some other words to catch the right people. Just to say "copper coin" is so vague.
Done.
css, about the hand wipes, thanks. But I have to see what I can find here in the region.
I'm analyzing the options for now, but something I must do, can't let that relic covered in green rust (it was minted shortly after our independence).
I have learned to use home vinegar plus salt to remove verdigris, the green stuff. I have really old Chinese copper coins, some more than 1000 years old, and when I got them they were totally green, not possible to identify.
I put few coins to the vinegar-salt liquid, keep them there 10-15 min, stirring sometimes and watching what happens. But please be careful especially if the coin is more valuable. Are you sure of the metal and metal content, because if it is not totally copper (have tin or zinc), as some of my cast coins have, then this method could change the color of your coin. I don't remember was it tin which causes the color effect.
Quote: "Ollisaarinen"I have learned to use home vinegar plus salt to remove verdigris, the green stuff. I have really old Chinese copper coins, some more than 1000 years old, and when I got them they were totally green, not possible to identify.
I put few coins to the vinegar-salt liquid, keep them there 10-15 min, stirring sometimes and watching what happens. But please be careful especially if the coin is more valuable. Are you sure of the metal and metal content, because if it is not totally copper (have tin or zinc), as some of my cast coins have, then this method could change the color of your coin. I don't remember was it tin which causes the color effect.
Please tell me more. What proportions of vinegar and salt?
And as far as I know the coin is only copper (link for profile on first post).
By the way, I received one of these "all green" coins you mentioned (a 350-year-old polish-lithuanian copper), not well preserved but (mostly) readable. Could try with it first.
I'm not personally a fan of any sort of vinegar on copper. There's a risk of turning the copper pink. I've seen some good results with it but I'm too much of a chicken to try myself.
Quote: "MonaSeaclaid"I'm not personally a fan of any sort of vinegar on copper. There's a risk of turning the copper pink. I've seen some good results with it but I'm too much of a chicken to try myself.
I have experience on this. But only on common coins without verdigris.
Usually a bit of lemon juice will do the job. However i must stress that after its "clean" you need to rinse it with water ASAP otherwise the coin WILL corrode and be destroyed. I sugest you do test runs with pennies until you get the hang of it. If that feels too extreme there is always the rubdown option with liquid laundry detergent or ketchup.
Quote: "ebec89"Usually a bit of lemon juice will do the job. However i must stress that after its "clean" you need to rinse it with water ASAP otherwise the coin WILL corrode and be destroyed. I sugest you do test runs with pennies until you get the hang of it. If that feels too extreme there is always the rubdown option with liquid laundry detergent or ketchup.
I have experience using lemon. But will it work with a verdigris so severe that formed a crust?
I've done it.
Lemon and vinegar. The result was not perfect, but 95% of the verdigris is gone. Only 2 tiny green patches remained, and after the cleaning I've seen small verdigris corrosions where the crust was thicker.
The higher parts became brighter and the lower parts (background) remained dark. It lost value by ending cleaned but gained value for being verdigris-free (or almost). Well, I paid half of its medium price. At least its easier to read as the letters got more contrasted. And revealed the full coat of arms.
Success rate: I'd say 60%, not a total success but not a total disaster.
And same mixed success for the smaller coin, more worn but more visible. Almost forgot, its ID: https://en.numista.com/catalogue/pieces119301.html.
