...but slabs are not airtight. Coins can, and do, deteriorate in slabs. In fact some unscrupulous sellers on ebay buy slabbed coins and artificially tone them, trying to make a larger profit, by putting the slab in a container with a source of sulfur.Well you could always buy ancient coins that are already in slabs :). Then you wouldn’t have to worry about deterioration.
I am a former high school Chemistry teacher.Yikes! I never use acetone or any chemicals on coins with numismatic value.
Acetone is perfectly safe for coins (and people - as Dr.s well know - an overdose is treated by waiting for it to clear itself out of your system!). It will remove many surface contaminants and cannot chemically alter/change/dissolve/discolor/french fry/chocolate coat etc. your coin
All acetone will completely evaporate off of the surface once the coin is removed from the bath. Room temperature is too hot for acetone to remain in liquid form...which is why it feels cold to the touch...its evaporating as you touch it.
I have used it on many hundreds of coins for over 11 years with absolutely no side effects, and again, its b/c the acetone is not there. It did its job and evaporated totally off of the coin when removed form the bath.
Note it must be from a bottle labeled as pure acetone.