Patina work involves putting the final color on the bronze, using a large blowtorch to heat the metal up, and spraying on the secret alchemical formula. Bronze is mostly copper but is quite a bit lighter orange hued than copper. It’s very reactive so tarnishes and stains and turns green or brown outside quickly. The patina I favor is a red that is said to be the most stable of all bronze patinas.
In these photos I’m putting on a first patina application. The metal has to be around 200 degrees F or near the boiling point of water, so that the chemical steams off. The temperature is pretty critical, and if the metal isn’t hot enough the solution just dribbles down the surface and pretty much ruins the patina. So you quickly learn not to let that happen. And that explains the foil, which protects the cold surrounding metal from overspray. I now use an infrared electronic thermometer that can just be pointed at the surface to get a readout of the temp.
Later I decided the color should be a bit deeper because outdoors it looked much paler than under the studio lighting. So another entire layer was applied. It takes about a full workday to do one layer on a sculpture this size.
Both the bronze and the stainless pieces in these photos have what I call a textured or “parrot’s feather” surface. This is engraved into the surface with the edge of a disc grinder. The heavy 7″ grinder has a coarse cardboard disc with a hard rubber backing pad. First the pebbly mill finish of the plate stainless steel has to be ground away. Then the edge of the disc is used to lay down bands of layered wavy lines of arc shaped grinding marks. Up close it resembles feathers.
The stainless for this particular sculpture is just left the natural silver color. I also use this surface for stainless and bronze sculptures that get colored with a patina in some way, either through just heat treatment or with heat and chemicals. The texture not only makes the surface very lively and reflective, it can also result in a variety of different colors coming through.
The other shots here are of welding the stainless sculpture to it’s base, and engraving the signature. Signing it means it’s done, so that’s always a great moment, believe me, when you sweat over a piece for a couple of months.
Below is a short video showing some of the work being done on K2. I don’t have titles yet, and despite the number, this is actually the last of the five sculptures to be completed for the project. The other three large sculptures are currently being ‘detailed’, fussed over and patinated, which takes some time. But it is good to have the major construction of them all finished.
I’ve been asked how the ‘engraved’ surface finish is applied so I chose some of the footage to illustrate that. We have taken some good film throughout the design and execution of this sculpture project that will be made into a short documentary sometime in 2012.