An overview of the patina process 

The "patina" is the color of the bronze. "Patinazation" is the process in which a calculated chemical reaction between bronze, acidic chemicals, and high temperatures oxidize the surface of the metal. Certain chemicals will produce certain predictable colors when they are applied to heated bronze.

The patina process begins by heating the surface of the bronze with a torch.  Various chemical solutions are prepared and applied with a wide variety of techniques, the most common being done with natural bristle brushes and spray bottles. Chemicals can also be applied with spatter guns, and airbrushes.   The applied finish is then coated with wax, clear lacquer or a combination of the two.