In some instances where a copper effect is desired, it may be preferable to simulate copper than to actually use it, due to the rapid tarnishing that occurs in copper. The look of copper can be simulated with other metals by using a technique known as a patina. This technique chemically seals the metal with a decorative finish, preventing corrosion. Hot patinas are applied to metals using a propane torch. Aluminium, bronze and iron are excellent metals on which to use a patina.
Take appropriate safety precautions. You will be working with both heat and chemicals. Wear long sleeves and safety goggles to prevent injury from splashes. Depending on the type of chemicals in your patina, you may want to wear a respirator. Wear heat resistant gloves to avoid accidental burns.
Clamp the metal object to your working surface. Because the object will be heated to a high temperature, you want to avoid holding it. Position the object within the clamp so it is suspended in the air and does not directly come in contact with the table.
Light the propane torch.
Heat the metal object with the torch. Slowly move the torch back and forth to ensure that the metal is heated evenly. This will create a surface for the patina to adhere to.
Apply the patina chemical with a brush. Numerous copper-coloured patinas can be purchased commercially; experienced metalworkers often make homemade patinas.
Heat the patina with the torch. The heat is used to increase the rate of oxidation in the metal, forming a chemical reaction that changes the colour of the surface. This change takes place before your eyes, and you can control the effect. You can create artistic weathered looks by adjusting the amount of patina and the heat. Continue to apply the patina as needed.
Seal the patina to prevent further changes. One sealing technique is to apply a thin layer of hot wax to the finished object with a brush; you can also use a lacquer.
Be sure that the propane torch is completely shut off when you are finished working. If the torch valve is open but not lit, it can emit propane gas into the room. Work in a well-ventilated area. Chemicals can be dangerous, so you want to minimise contact with them.