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Coins won't care about ambient temps around 10% of their metal's melting point. I'd be more worried about the packaging,
I agree. I haven't done the experiments, but generally speaking the rate of chemical reactions doubles for each 20 degrees F. So, if a coin sits in a hot mailbox for a day, you would expect that surface reactions like toning would speed up a bit for that time. 8 hours at 150 F would come out to being equivalent to a week of time at normal room temperature.
If the coin is in a plasticized PVC flip, we are talking about something different: the rate of migration of the plasticizer out of the plastic (not a chemical reaction). Temperature will also speed up this process, but not sure by how much. By the way, all plastics (even polyethylene) have additives that will slowly migrate out to the surface of the plastic (it's why you are able to easily unscrew the top off of a bottle of soda). But some have more than others.
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Posted 07/26/2018 1:11 pm
