Wear gloves and eye protection
Wash the copper with warm water and dish soap
Rinse and dry thoroughly
Apply white vinegar and salt with a soft cloth
Rub gently until oxidation lifts
Rinse off residue with clean water
Dry completely with a soft towel
Buff with a microfiber cloth
Use lemon juice and salt as an alternative cleaner
Use baking soda and water paste for stubborn spots
Apply a commercial copper cleaner if needed
Polish with a copper polish after cleaning
Seal with wax or lacquer to slow future oxidation