Here's how to verdigris copper easy and using no toxins:

1. Rub a mix of salt and vinegar on the item.

2. Place in a closable box with a small container of fresh ammonia.

3. Leave for a while. It turns all cool.

4. Wash it off; as it dries it re-verdigris.

5. Seal it using a very thin layer of acrylic floor wax.