The vivid warmth of a gleaming copper roof adds a unique charm to your home. Unlike other roofing, however, your copper roof may turn dull, brownish or even black, so that you will want to clean it. Follow these directions to use a chemical or natural cleaner to restore your copper roof to its original new-penny gleam.
You can clean copper with a chemical-based cleaner such as Brasso, but you will need a large amount for a roof. Ask at your building supply center for a large-volume container of this cleaner. Apply it with soft flannel cloths over your roof starting from the top, in a thick film. Allow it to dry overnight, or for at least six hours out of direct sunlight.
After it dries to a white powdery finish, put on a pair of smooth old leather gloves, and with fresh flannel cloths, buff the entire surface from the top down to remove all the powdery residue. Use a soft toothbrush to get the cleaner out of cracks and under edges. When it is shiny again, coat it with a layer of polyurethane so it will not oxidize again. You may need to recoat it every two to three years.
Two effective cleaning pastes for copper are made from ingredients in your kitchen. One contains 3 cups pure lemon juice, 1 cup white vinegar, and salt; in the other the lemon juice is replaced by all-purpose flour. To use the lemon juice-based cleaner, mix the three ingredients into a large bucket and stir till the salt is dissolved. Dip an absorbent cloth, such as an old towel, into the cleaner and wipe it over the copper surface, from the roof peak downward. Use a firm natural bristle scrubbing brush to scour the copper surface. Rinse off the cleaned area with a garden hose while you are scouring. The liquid will run down the roof and help lift off more staining from the lower areas. When you have scrubbed and rinsed the entire roof, allow it to dry. Avoid touching the clean roof with your bare hands, as your skin oils will leave a dark patch on it.
For the flour-based cleaner, mix a solution of 1 part flour, 1 part vinegar and 1 part salt, in a large enough quantity to cover your entire roof with a uniform layer. Allow it to dry overnight or for at least 6 hours. Rinse the paste off the roof in the morning with warm water and dish-soap solution. Rinse the roof again with warm, clear water to flush away all the soap residue and dirt. Buff the roof with a clean, soft flannel cloth to bring up the shine.
Preserving the Coppery Shine
If you want to retain the freshly revealed copper shine, spray or roll-paint the entire roof with a clear lacquer or a clear polyurethane coating. If, however, you want your copper roof to develop the soft green patina that copper naturally gets when oxidizing, you can apply a specially designed safe coating that simulates that "aged copper" finish.