To patina a copper roof, first clean the surface before applying a mixture of ammonium chloride crystals dissolved in water. Apply lemon oil periodically for maintenance.Continue Reading
Clean the copper surface using a commercial metal cleaner. Oil, grease and dirt arrest the chemical action needed to patina copper artificially. Rinse thoroughly with water to remove all traces of the cleaning compound.
Dissolve ammonium chloride crystals in water until no more dissolve. Create the mixture in a corrosion-resistant, plastic-lined container. Let the solution sit for 24 hours before application. Be sure to wear gloves and other protective gear when preparing the solution.
Carefully pour the solution into a plastic sprayer, preferably one with the interior coated with bituminous paint. Spray the solution rapidly on the roof, and allow to it to dry. Wait 48 hours before spraying a second coat.
Wait 24 hours after the second application, and then spray with a cold water mist. Do this in dry weather for the best results.
Apply lemon oil to the roof to stop the weathering process once the desired color is achieved. Apply it additionally once every year, or once every three years in wet climate areas.