How to Turn Copper Roofing Green

What You'll Need
Protective gloves, mask and goggles
Cleaning brush or sponge
Sulfuric acid
Cuprous chloridelhydrochloric acid

Copper roofing is bright pink to begin with, and in time, it can gain a brownish color and then a nice blue-green patina. The patina is due to the process of oxidation and the sulfur particles in the atmosphere. This process will take several months or years, depending on the atmospheric conditions in your area. If you want to obtain this green patina in a day, you can use a patina agent on your roof.

Step 1 – Clean Your Roof

Before attempting to apply the patina agent, you will have to clean your roof to remove the dust, debris and other possible substances that may have gathered here. If you apply the patina agent on a dirty roof, your roof may have a stained appearance. Use some diluted detergent and a brush to clean the roofing, and then rinse thoroughly using buckets of lukewarm water.

Step 2 – Remove Oxide Layer

If your roofing is brand new, skip this step.

If your copper roof has been exposed to the outdoors for over 6 months, there may be a thin layer of oxide, which you have to remove. If the oxide is not removed, the results may be poor, and the patina agent won’t adhere to the surface. Use diluted sulfuric acid to clean this layer (use 100 ml of acid in 1 liter of water or you can get 5 or 10 percent sulfuric acid directly from a hardware store). Make sure you wear rubber gloves, a mask and goggles, as the acid is toxic if inhaled and will also cause severe burns if it comes into contact with skin. You should also protect your clothes, as they can also be affected by the acid. Don’t store the sulfuric acid in metallic recipients, and use only plastic recipients or buckets, which won’t react with the acid.

Step 3 – Prepare the Patina Agent

The cuprous chloridelhydrochloric acid can be prepared at home or purchased from a store. If you prepare the solution at home, you will need:

  • 150 g of cuprous chloride
  • 75 g of ammonium chloride
  • 10 g of arsenic trioxide
  • 100 ml of HCl
  • 50 ml of glacial (water free) vinegar
  • 1 liter of warm water

You will need more than 1 liter of water (20 to 25 on average), so multiply the needed amounts of ingredients with as many liters as you need. Don’t use a metallic container when preparing the solution; opt for plastic.

Step 4 – Apply the Patina Agent

Use a brush or a sponge and apply the patina agent. Wear protective gear, as the solution can cause irritation. When applying the patina agent, you can obtain various finishes; experiment with your brush or sponge on small portions of copper roofing to obtain the desired finish, and then apply the patina agent on the entire roof.