I'm not sure this is the proper subcategory but seems the closest to me.
I've
had a half dozen coin soaking in distilled water for months. They are all really
poor shape so more of something to do than an active project.
After these few months, the coins started looking dry and ugly so I placed them in a
bowl of olive oil (can't call it virgin cuz already been used soaking other coins in the past - sorry bad attempt at humor).
Unlike the water, changing it every few days these
sat in the olive oil for about 2 months forgotten.
Today I took a look at them and the oil turned blue.
I pulled one coin out and wiped it - looks nicer than the "dry" look from soaking in water, this disturbed the blue. Originally it was just close to the coins - pulling the coin spread the blue around.
Anyone know why? What would cause the olive oil to change to blue?
Thanks for the chemistry lesson in advance.
John