Reason why I'm asking is because there is a thrift shop by me that sells coins. Problem is they put price stickers on all them. A lot of the coins are cheap but there are some that were a bit more valuable. Last time I went they had just gotten in some new coins including 2 cent pieces and some world silver coins. All of them had stickers on them. I purchased a few after carefully peeling the sticker off but noticed some glue still on them. The funny thing is after I mentioned the glue on them, the owner wanted to clean them with Windex. I had to clean off the spots of glue with warm water and a q-tip. But the though of all those other coins and whatever new ones they bought in came in my mind. Lets say that if no one was to buy these within a year, would the glue on the sticker damage the coins?
A lot of eBay sellers do this too - they tape the bare coin to a piece of paper to ship it. It annoys me but I'm mostly buying lower quality coins so I haven't noticed any lasting damage. Some tape/stickers are worse than others of course.
Yes, it would. Tape, stickers, glue, those things will leave lasting marks on the coin after a period of time even if you remove the substance itself. Typically the area where the tape or glue was will be lighter in color than the rest of the coin. That's why when you see a coin that looks like it has a stripe across it, but there's nothing on the coin, you always know that coin used to have a piece of tape on it.
Sticker glue is obvously not good for coins IMO you should notify the thrift shop that pressure sensitive adhesive used in their stickers is harmful to coins (especially in the long term). Maybe you can sell them some 2x2s or non-PVC flips. You may consider soaking any coins you have purchased in pure acetone to gently remove the residue. If Acetone doesn't dissolve the adhesive, then emersion in Alcohol may help to lift the adhesive. Sometimes you might need to gently work away the adhesive while the coin is immersed in the Alcohol so that the Alcohol gets under the adhesive. There are several pressure sensitive adhesives that cannot be cleaned by either Acetone or Alcohol. IMO most coins that tone with adhesive on them look terrible.
I did tell them and thats when he mentioned he wanted to clean the coins with Windex. Of course I told him not to and just don't put stickers on coins in the future. And I doubt they will buy 2x2s from me unless I donate it to them.
I think you pretty much summed it up. Places that don't specialize in coins treat coins like typical pocket change. You could try showing them how cheap the 2x2s are, and that it may draw more serious customers if you treat coins in the proper manner (like not using Windex).
This thrift store likely got the coins for super cheap or near nothing, likely dealer bought prices or even cheaper. If they don't specialize in coins nor care, as long as people buy them at the prices they set, they're never going to care. More money is their motive, not specializing in one area of likely everything else they can sell which is literally anything that they deem could make them profit.
The adhesive itself probably will not harm the coin at all, but as Doug said the area under the adhesive will not continue to tone or oxidize at the same rate as the rest of the coin. This means that if you leave the adhesive on long enough eventually even if it is removed you still see where it was because of a difference in the coloring. So it is best to use some acetone and get the sticker residue off of the coins as soon as possible.
Looks like I'm going to be experimenting with Acetone then. I might need to play around with cheaper coins first to get the hang of it.
So you bought some of these coins with stickers on them ? It's not advisable to do that, but if you did, what's done is done. But what kind of coins are they ? I ask because while silver and clad coins will be OK, copper coins sometimes have less than desirable results with acetone. They can turn weird colors later on. Either way, this may be helpful - http://www.cointalk.com/t193708/
You might try going to the thrift shop and saying that although you probably don't want to buy all the coins that come their way, you might like one or two, and you just prefer not having to try to get sticky stuff off coins. Then give him about 20 flips, and ask that he put the coins he sells in there, with the price sticker on the flip. Tell him that even if you don't buy a particular coin, he probably will sell more if he uses the flips. And find something to donate to that thrift store...paperbacks, used t-shirts, whatever. Being nice goes a long way (even though I can't claim to be the nicest person all the time).