Ancient copper can get lovely blue patina, in the right environmental conditions.
Photo of statue of liberty on courtesy of WIKIPEDIA.
You can age a copper dish or jewelry by giving it blue patina. There are commercial agents for that,but you can do it with household salt and vinegar
Vinegar is my idea of "magic potion". My family members hate the smell of it, because I use it all over.
Tips on using vinegar: http://www.versatilevinegar.org/usesandtips.html
Steps of making blue patina on copper:
Cleaning the copper:
First, clean the copper using dish washing liquid and wash with tap water .
Sprinkle some baking soda over it.
Scrub the copper with steel wool.
Wash with tap water.
Dry with paper towels. Avoid touching it with your fingers.
Vinegar and salt solution:
Mix 3 tablespoons of salt with 6 tablespoons of vinegar in a small bowl.
Most of the salt will not dissolve.
Put the copper in the liquid. It should be all covered.
Let it soak for an hour.
Take the copper out and put on paper towels. Do not wipe the copper. It has to be dried naturally.
Sprinkle some salt on.
Leave it to develop the patina.
If you want to enhance the process, dip a paper towel in vinegar and
lay on the copper.
Let it stay on until you are happy with the patina created.
Because some of it will not stay on, it is better to have more patina than you like it to have in the end. This might be taking a few days .
Take the paper off. Let dry.
Below you can see what I got after 24 hours of salt-vinegar treatment.
Gently rinse with water. If you want to remove more patina, use steel wool.