Copper flashing tends to be more expensive than some flashing products, perhaps because it is an attractive material popular among some schools of home design. However, as copper flashing ages, it can start to tarnish and look unsightly, although some home owners appreciate the green patina of aging copper. However, this tarnish can eventually eat through the copper, compromising the primary purpose of the flashing, which is to protect the interior of the house from exterior elements. It is important to clean copper flashing periodically to remove harmful corrosion and tarnish, leaving behind the aged patina which many find attractive.
There are several ways to clean copper flashing, depending on whether or not it has been sealed in a lacquer. If the copper has not been lacquered, it probably should be after it has been cleaned, to protect the metal and make the flashing longer lasting. While copper is durable, it is subject to corrosion, like most metals. The first step in cleaning copper flashing is determining whether or not it has been lacquered. If the corrosion is not bubbling up out of the copper, it has probably been lacquered, and should be cleaned with warm water and soap only so that the seal is not damaged.
If the lacquer has begun to wear off, it should be stripped so that the copper can be cleaned and the lacquer can be reapplied. Lacquer can be removed by rubbing the flashing with rubbing alcohol and allowing it to dry fully. After that, warm water should be used to rinse the alcohol residue off, leaving behind clean flashing. Then the flashing can be rubbed with an acidic solution, buffed, and resealed.
To clean copper flashing with an acidic solution, mix vinegar or lemon juice with salt and apply with a damp cloth. This technique removes tarnish with the acid, while gently abrading it with the salt to remove unsightly bubbles of corrosion. Afterwards the flashing should be rinsed with soap and warm water to make sure that no salt or acid has been left behind. The flashing can be buffed with beeswax or another oil to bring out the shine and add a protective layer to the metal.
Many companies sell seals and lacquers which can be applied to dry, clean copper flashing in order to protect the metal against the elements. These lacquers should be stripped and reapplied every few years or as needed to ensure even protection of the expensive and attractive housing material. Homeowners should also be cautious about where copper flashing is installed, because it can bleed onto other materials, particularly wood, leaving an unsightly stain.