What is patina?
Patina is the thin layer formed on a metal’s surface, produced by its reaction with chemicals in the environment, giving its tone and colour. Over time copper will naturally react to air and moisture present in the atmosphere and, due to the high copper content of bronze, sculpture made from bronze will react in the same way. During the production process, different patinas are achieved on bronze sculptures by applying specific chemicals with heat. The applied patina enhances the form and texture of the sculpture and compliments the piece overall.
Traditionally, a thin layer of beeswax thinned with benzine is applied to protect the patina and prevent further chemical reaction taking place. After waxing, the patina should remain fairly stable if properly cared for, however, as patinas are organic, they may change slightly over time even when properly looked after. If you become concerned about changes to the patina on a bronze sculpture it is advisable to consult a professional.
How to maintain your bronze:
Remove any dust or grime from the sculpture using a soft cotton cloth. If there is an unusually thick layer of wax or grime, mineral spirits may be used to gently remove the excess.
When the surface is clean and dry, a thin layer of beeswax (thinned with benzine) can be painted on with a medium to hard-bristled brush. It is important to cover all areas including crevices and undercuts. The wax should then be left for at least five minutes to settle and harden.
The wax surface can then be buffed with a soft cloth to give the patina a rich lustre. A shoe-polishing brush or paintbrush may help to remove excess wax from grooves or a rough texture.
For indoor bronzes water, direct sunlight and contact with household cleaning products such as Windowlene, Brasso, Handy Andy etc. should be avoided.
Outdoor bronzes are more susceptible to environmental factors such as rain, sunshine, plant resins, etc., and should therefore be cleaned and waxed on a more regular basis, usually at least once a year.