Thanks, everybody, for your suggestions.
I did a little experimenting in the mean time, boiled the coins in plain water, boiled them in washing soda, but every time I took them out of the
bowl with cold water after the boils the water
still came off in little beads and pearls. I guess the sealant is some kind of commercial wax as simple mineral oil should have been dealt with by now. One of the batch has now become the sacrificial
lamb and I will immerse it in acetone. In my readings I did not find anything that wold indicate an adverse chemical reaction with CU - of course, I don't know anything about the chemical proprieties of the sealant used.
I'll let you know what happens.
Generally, do you recommend sealing coppers or bronzes? I never bothered, and it never occurred to me to check all those
Elymais bronzes I have for a sealant. They do not have deteriorated in their case but I do have a dehumidifier in the room they are stored in. If you buy a bronze from a rather well known dealer in that particular
field do you assume automatically that they have been sealed?
Wondering,
Schatz