Thanks for your response. I don't keep the coin in the freezer-just cool it briefly. I would not want water to freeze in any minute cracks in the
flan or I could end up with a split coin.
Nor do "shock treat" the coin by dropping it in water that is already boiling. I would
hope that the
flan has a different expansion coefficiant than the crud. You may be right, it hasn't
had much effect on the crud. The black
patina can't even be scrathed with the
dental pick though I have been able to get some thicker spots off with it. Do you think there is any detail in the emporer's cloak? With this
type, the folds are defined by some raised lines, and not modeled realisticaly like on earlier coins, even late
Roman bronze. I will post another pic if I make significant progress.