Bronzes are made from the powders resulting from the forging metals, mainly copper, iron, zinc, and tin. The powdered metal in the course of preparation is ground and heated with a little oil, grease, wax, or paraffine, and the resulting superficial oxidation produces the bronze. Some bronzes are also made by a solution and precipitation of the metal in a finely divided state. Bronze powders are largely imported from Germany and England. Of gold bronze, there are but three varieties of consequence, but sold under a variety of names, and prices to correspond. Radiator, or cheap bronze, a medium grade, and leaf bronze. The better bronzes are usually more finely powdered and should be more brilliant. Bronze is judged by its color, lustre and fineness. For fresco work, brilliancy is the all-important feature, and may be present to a more marked degree in a cheap bronze, than in a better grade. Aluminum bronze has largely taken the place ,of the so-called silver bronze, as aluminum is less apt to tarnish than the metals used in making the ordinary silver.