Green Stuff on Copper

What are the uses for dichloromethane?
The greatest use of DCM is as a paint remover. Other uses include: solvent and cleaning agent in chemical manufacture, textiles, electronics, metals and plastics, pesticides industries; blowing and cleaning agent in the urethane foam industry; fumigant for strawberries and grains, and as degreener for citrus fruits; in pharmaceuticals and as an anesthetic; in extraction of caffeine, cocoa, fats, spices and beer hops; as a heat transfer agent in refrigeration products.

I’m not putting something on my coins they spray on green citrus fruit to MAKE it de-green. Is it going to make my Mint State Red copper coins de-red?
Sorry not going to happen!

 

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Holy Crap, check out the MSDS for this stuff. Absorbed through the skin, known carcinogen. Unless you have a chem lab in your house, I wouldn't mess with it.

http://www.sciencelab.com/msds.php?msdsId=9926060

 

Yup kind of reckless to recommend a heavy carcinogenic chemical without any regard to how it might be handled safely. Might as well recommend using liquid cyanide and have them drink water out of a similar glass at the same time. Didn’t work so well for one chap back in the day but results may vary.

DO NOT DO ANYTHING I POSTED ABOVE!

 

Looks like the surface under the corrosion is going to be etched. Put a drop of Coin Care or Verdi-Care on the ear and blot it away with a Q-tip. Follow with acetone to remove the chemical. Your coin should still be etched. Unfortunately, something that can be fixed in a few minutes at a conservation service is too hard to explain or suggest w/o seeing the coin.

 

Thanks Insider...I was thinking of trying that first...spot treating with saturated tooth pick...maybe dissolve a drop on the spot for a few minutes and then start digging. If I get nowhere, I'll soak the whole coin. Something like that. If that fails, I'll have to get some DCM and a mask

 

Exactly. Once they can find a suitable replacement, it will not be used as much. Works better than acetone on pvc though. It's good to be a chemist.

 

I have cleaned Mint Red 1909-S VDBs with it. It doesn't change the color like acetone will, nor leave any residues. I have dealers at every show asking if I brought some with me because they have a coin with pvc or cloudiness.

 

Is this stuff hard to come by?

 

I've been using Acetone to remove PVC residue from coins ever since they stopped making CFC113 in the 80's and never had a copper coin change color. As far as I've been able to tell, the only research indicating that acetone can directly react with copper is the following paper:
http://www.stonybrook.edu/vescalab/research/research7.html
They soaked copper in acetone for 18 hrs, and after the acetone evaporated, found copper acetate crystals and an odor of acetic acid. The authors even comment that the formation of acetic acid is a slow reaction. Do you know of any additional research that discusses this reaction, or the reaction rate for the formation of acetic acid in the presence of copper? Dipping a copper coin in acetone for a few seconds/minutes and then rinsing, is a lot different than allowing it to soak and evaporate over 18 hrs.

Unless there is something in the reaction rates that indicate a short soak would expose a coin to enough acetic acid to cause discoloration, I really wouldn't want to trade the risk of using a using a potentially hazardous solvent like dichloromethane for a much safer solvent like acetone.

Since you're a chemist, I'm sure you're proficient with the safety procedures for handling this type of material and don't dispute that it gives you excellent results. But how are the vast majority of CT members, who aren't chemists, going to make an informed decision about the risks of using a hazardous solvent versus the risks of discoloring a copper coin with acetone, especially since the latter risk appears to be insignificant?

 

Acetone won't touch this verdigris

I've experienced acetone changing the color of copper coins but i believe the acetone is interacting with unknown surface contaminants on the coin. Who knows what's on the coin when you drop it in the acetone.

 

VerdiCare will just let it soak.

 

Holy cow! I just put it in to soak a half hour ago...figured I'd let it go overnight...just checked and it looks almost gone already! Will post pics soon

 

Green is gone. Discolored beneath--which stinks. Looks like luster has been eaten away. There is some black (neutralized verdigris, I believe) that's deep in the ear that I've been picking at with toothpick. Really tough stuff. Going to soak overnight. Hopefully I can get that totally removed and the discolored area will tone over time to become less noticeable. Anyway, Verdicare is worth the price. I have a ton of coins that need the treatment. Looking forward to seeing it's results