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 Replies: 26 / Views: 2,244 |
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Bedrock of the Community
 United States
19951 Posts |
I will do that. I'm a Chemist so I have access to the highest purity reagents you can get.
Thanks
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Valued Member
United States
282 Posts |
Hey BadThad, If you are a chemist use MEK instead of acetone. It works better and faster. It is just harder to get.
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Bedrock of the Community
United States
19951 Posts |
Will do, thanks Gary.
Anybody know the composition of this green "stuff". It should be a copper oxide, which should not be soluble in organic solvents like acetone. I'm surprized any of you have sucess at removing it with acetone.
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Pillar of the Community
United States
3234 Posts |
Denatured alcohol works wonders. However, if the corrosion is really in the metal then nothing short of a brillo pad will remove it in any bit of decent time. You could try extra virgin olive oil for about 1 year and see what happens. Sometimes the corrosion isn't really in the metal so much as the dirt itself is showing the green. The alcohol will lift the dirt and the green goes away. Nothing stripped on the coin, the patina remains, and there should be no noticeable residue.
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Bedrock of the Community
United States
17884 Posts |
quote:
Anybody know the composition of this green "stuff". It should be a copper oxide, which should not be soluble in organic solvents like acetone. I'm surprized any of you have sucess at removing it with acetone.
You're a chemist so you'll understand. Most of the people here and on other forums. when they talk about "green stuff", are just talking about green stuff. They have no idea what it is made of and use the term for anything on a coin that has a green color. If it is true verdigris, A green often fiberous looking substance, then you are right the organic solvents won't touch it. The best you can hope for is to use the acetone to remove other trace contaminates and to dry the area which hopefully will stop further corrosion. A great deal of the "green stuff" will be called "PVC contamination" even though there is no PVC in it and the coin may never have been around PVC. If it does come from being around leaching PVC flips and you have true "green slime" then what you have is copper chloride in an oil suspension. Naturally the organic solvents will work well on this as it dissolves the oil and disperses the suspension even further. In a great many cases the "green stuff" is just normal circulation dirt, skin cells, skin oils, and possibly a little lubrication oil. The solvents work great on this stuff as well. |
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Bedrock of the Community
United States
19951 Posts |
Thanks for the info conder101. I was thinking of putting on the SEM/EDXRF to determine if it's organic or not....I think I will now because I'm very curious about the chemical make-up of coin debris.
If you search the forums, you'll see some EDXRF scans I posted on a white, hazy layer on one of my proof Kennedy's. Oddly, it showed as a copper oxide (but it's a white film), but I've been unsucessful at removing it using a LOT of different methods. It's a proof coin, so I've been trying to avoid anything too harsh like mineral acids.
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Bedrock of the Community
United States
19951 Posts |
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Bedrock of the Community
United States
17884 Posts |
Possibly a thin film of copper carbonate? In a thicker film the green color would be apparent, but in a thin film it could have a whiteish appearance. It would also explain the Oxygen spike on the graph as well.
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Bedrock of the Community
United States
19951 Posts |
That's an excellent guess considering the presence of carbon. If it is a carbonate, it should be removed with acid fairly easily. However, I've already tried dilute acetic and citric acids to no avail. I've been trying to avoid the use of mineral acids, I fear they may damage the good side of the coin, but I still may resort to them in the interest of science.
Thus far, everything I've tried doesn't work, the film is really well bonded to the surface. I've even tried using aluminum with a hydroxide catylst and organic solvents do nothing.
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Pillar of the Community
United States
2443 Posts |
Nice! Thanks for remembering to post a pic.
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Bedrock of the Community
United States
19951 Posts |
Thanks Amazon, I'm glad you and everyone else enjoyed the pictures. |
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Replies: 26 / Views: 2,244 |
First Page
Posted 08/16/2007 11:43 pm
