Hi, often I encounter coins that I clean that are covered in either a white/tannish coating or a black coating. This is definitely not the patina, but rather a sometimes fairly thick coating on the coin.

I have begun wearing masks because it leaves a bad taste in my mouth. It is almost a chemical taste is the best way I can describe it.

Do sellers sometimes apply a coating of a chemical or some kind of protective layer on coins that they would mark as a uncleaned coin lot for sale

I have cleaned many coins that have dirt and crustaceans on them and even some calcium deposits that are hard like a rock, but this is different.

A particular note, a recent batch I received from Spain that were Pirate coins were particularly nauseous and irritating and definitely a chemical taste.

I’m just trying to find out what I’m dealing with here.

Thanks.