i think it was the Egyptians who invented plating. it is done by suspending a metal within a liquid. often using an acid to do so. then the object that is to be plated has a positive and negative electrode attached to it. then it is suspended within a tank of the "liquid metal" and a current is passed thru it. the molecules of metal are drawn to the electrical current and stick to the item that is emitting it. the longer it is left in the thicker the plating becomes. you can tweak the current to get odd build up as well. some of this bubbly looking stuff was probably done on a higher current, causing it to build up faster and ball up. it's actually a really simply process.