How can I achieve a purple patina on copper?

To achieve a purple patina on copper, you can use a combination of ammonia and salt to create a chemical reaction that will oxidize the copper and produce the desired color. This process can be done by placing the copper item in a sealed container with a small amount of ammonia-soaked paper towels and salt, allowing it to sit for a period of time until the desired patina is achieved. Remember to wear gloves and work in a well-ventilated area when working with these chemicals.