Bronze Casting - Final Sculpture

Most - but not all - bronze sculptures have a "patina" added. This is a coating of chemical compounds which gives color to the bronze. This sculpture was patinaed with "liver of sulfur" (called "liver" by the cognoscenti) which is a mixture of various potassium compounds of sulfur, but largely potasssium thiosulfate. When the sulfur compounds are heated beyond their decomposition point on the bronze surface, they form copper sulfide - which can produce anything from a smoky copper color to a think velvety black. Needless to say, you also get some hydrogen sulfide off, which is unaesthetic at best and a health hazard to boot. So do not try this at home.

Patinas can vary from rudimentary - a single color brushed over the entire sculpture - to elegant and patterned. The latter patinas generally require the hand of a specialists - called patineurs - who through years of experience know how to control both the application and the colors themselves. But in general, the technique is to heat the sculpture to a temperature where water will sizzle if brushed on. This allows the patina compound to remain on the surface after the water boils off and the heat of the surface produces a new compound - either a copper derivative from the bronze or an oxide (from being heated in air). As we said, using the "liver" produces black copper sulfide.

In this case the body and base were first patinaed with the liver and the horns left were unpatinaed (although a bit of the liver did splash onto the horns in various places). Then a solution of ferric acetate was brushed on (again onto the hot surface) which produces a light coat of red ferric oxide. The hoi polloi might refer to this patina as "rust" although it isn't strictly speaking quite the same thing. The horns were patinaed with only the ferric acetate.

After the sculpture cools down to where it is just warm, it is then given a thin coating of wax - thin turtle wax that you use to polish you car works fine, thank you - and then buffed with a soft cloth.

Then, voila!, you have a true bovine triptych masterpiece!