When do you need permission to sculpt or paint a famous person? I can understand if you do something of George Washington or someone from history. What bout someone like John Wayne, Tom Landry, Ronald Reagan, or someone like that?

Hi guys and girls
Working on a life size fairy at the moment, she will be naked dancing in a ring of magical mushrooms. Contemplating wings and a while ago saw some copper bowls made from very fine copper mesh, they had been treated with some form of acid which discoloured and ate some of the copper, the result was a truly beautiful fragility. Does anyone know what the acid might be?