Colouring metal has presented a dilemma to artists for centuries. Until recently, chemical solutions were the only way to change the colour of metal, and those colours were not bright. Now, with new materials, such as Prismacolor pencils, there are new fun and fascinating ways to brightly colour your metals. Copper is one of the best metals to use for this project because, compared to silver and gold, it is inexpensive and looks especially good when enhanced with colour.
Decide what pieces you will need and cut the desired shapes from your copper stock using tin snips or a jeweller's saw. Consider working on the pre-made copper shapes available at hobby shops. File the edges of the final shapes and drill holes for connectors, rivets, bails or wires. Many artists make holes which will be used to rivet their copper piece to a more "skin-friendly" backing, such as silver.
Roughen the surface of your raw copper shape with 60-grit sandpaper to make the patina, which will be applied later. The rougher the surface of the copper is, the better the patina will adhere. Wear gloves and safety glasses while cutting or abrading your copper.
Wash the copper pieces thoroughly with liquid dish soap and water; degrease further using alcohol on a paper towel. The metal must be completely free of oil from your fingers for the patina to adhere to the copper. Apply oil with an artist's paintbrush in a deliberate pattern if you wish to have copper showing through the final colours
Patina your copper pieces by painting on a commercial patinating formula, gesso, or liver of sulphur. Warm your copper pieces in a toaster oven before using liver of sulphur, let sit until desired patina is obtained, and rinse well. Debra Weld, who is a pioneer in this technique, suggests using JAX Green Patina for Copper because it leaves a rougher surface than other products. Let the patina sit for 24 hours before colouring your work.
Colour your patinated copper with Prismacolor pencils, which have a higher wax content than other coloured pencils. Use a thin coat of the lighter colours first then move up to your darker colours. Swab your work with turpentine to smudge the colour. Work the colour into your piece with an artist's paint brush and the turpentine. Be sure to clean your brush between colours, unless mixing colours is your goal, which can give a beautiful effect.
Bake the pieces for about 10 minutes at 135 degrees C. Spray the pieces with clear acrylic fixative. Sand lightly with 0000 steel wool, add more colour, turpentine, bake, and spray again until you achieve your desired colour or until the copper will not take any more layers of wax. Seal the colour with Renaissance Wax and bake it for another 10 minutes. Use a soft cloth to remove any residue. Buff and polish your pieces to finish them.
A toaster oven is best for this project, although a larger oven will work. A toaster oven dedicated to crafting is ideal. It can take practice to get good results.
Work in a well-ventilated area. Turpentine and Renaissance Wax can be toxic.