I was recently handed a bag of coins from a relative, mostly European, but with a set of old Canadian cents mixed in. There are some great coins, nothing rare but an interesting variety, dating back to the 1810's. HOWEVER....almost all the reverses are covered in glue. The glue is so old that parts of it flake off without much effort, but plenty does not. Can I hope to separate very old glue from coins by prolonged soaking in water? What other 'non invasive' tactics could be employed?
Most glues readilly dissolve in the Numismatist's Friend, aka pure acetone. Anywhere from a few seconds to a minute or two immersion in acetone in a glass bowl or cup should do the trick without the potential hazards of other cleaning methods. :thumb: The important thing is to use only the pure stuff, obtained from a hardware, paint, or home store and avoid using acetone based nail polish remover with its unknown additives. Follow up with a quick rinse in deionized or distilled water, and place on a soft cloth to air dry without wiping or brushing. Some people say acetone should not be used on copper/bronze, but I've never had any problems so long as I limit the immersion to no more than two minutes.
I used to work in paint. Acetone will kill pretty much all plastics, and cause no damage to metal. i LOVE the stuff.
I had some nasty effects with copper coins using acetone. Use it with precaution as well as, do it in a well ventaliated area! You don't want any sparks or fire near the area that you are planning to do this.
In addition, acetone will remove that nasty PVC from the old plastic flips. Just BE CAREFUL! It is highly flamable.
In addition to dissolving PVC and glue residue, does acetone do anything to remove the "yuck" on coins... the black stuff that coats your fingers as you're sorting through a roll? I know it does nothing as far as toning goes, but I happen to like toning, so I wouldn't want to disturb it. The dull, dirty film on the coins could go, though, and I'd be very happy.
It may remove it, it could also remove just about anything, but do you really want to use it? It will leave a residue, unless carefully and fuly rinsed, and the coins stink until the film is evaporated. I never heard of anyone using it for this purpose. Anyone else?
I don't know. That's why I was asking. I don't want to "brighten" or alter coins at all, I'm just wondering if there is a safe way to lift the dirt residue without changing the underlying surface of the coin. I don't know if this falls under the category of "cleaning" or not. The finger oils and dirt that accumulate over the years and leave the surface of the coin feeling greasy is akin to glue residue to me. If this falls under the broader category of cleaning, including dipping, wiping, polishing... then I'll leave the issue alone and simply enjoy my greasy, dirty coins as they are. Acetone seems generally accepted for dissolving crud off of coins without altering them, so I thought perhaps it could be used for this purpose as well. However, if it will leave a residue then it defeats the purpose.
I generally rinse a coin in three successive bowls of fresh deionized or distilled water, and I've never had any residue problem. Acetone is an organic solvent which will remove fresh skin oil that hasn't actually eaten into the metal, so it is useless against old fingerprints. Any organic component of the crud on an old coin will be dealt with by acetone, but non-organic residues will not be affected. For that same reason acetone will remove PVC residue, but won't erase any of the damage caused by leaving PVC residue on the coin for an extended period. The potential for unwanted residues is exactly why you should never use fingernail polich remover, or any other mixture of acetone and somehting else.
"The potential for unwanted residues is exactly why you should never use fingernail polich remover, or any other mixture of acetone and somehting else." Thanks, Satootoko. I never thought of that.
Just keep in mind that there are those who do not think acetone, even pure acetone, should be used on coins except when absolutely necessary.
The other danger of removing the glue (or any other crud) is that the protected area underneath the glue may not have toned in the same way as the rest of the coin, so removing the glue could leave the coin with splotchy toning.
Based on the run of this conversation, I will definitely try out some pure acetone for <2 minutes with subsequent repeated dunking in distilled water. These coins are not rare, and the glue coating in some cases is extreme. This last comment does make me wonder, the times I've seen coins with splotchy toning, if adhesive removal is what I am really looking at, particularily if it is on the reverse!
I have found that cloroform is about 10 times the activity of acatone, you can't even use a plastic container, glass only. It seem to do a wonderful job of removing oranic debris, leaving all tone and metal unhurt. Be careful with the fumes/and always have eyeprojection and gloves on. I used it other other day to remove a ton of glue on a coin that acatone would just not dent.