I am a new member to EAC. I have never attempted to clean a coin as I believe it was not a good practice. In the , EAC Guide to Early Copper's publication, page 9, Cleaning Coins is noted. I read that commercial cleaners "leave a thin film of protective lubricant". I have noticed this type of film on a couple of large cents that I have recently purchased. Thought it might be olive oil in nature. Is this type of cleaning to protect a large cent common amongst copper collectors? This is new to me and has me inquiring on the subject of cleaning copper.