About Bronze Form

The British artist Henry Moore is well known for his monumental outdoor sculptures, three of which are installed at the Getty Center as part of the Stark Sculpture Collection. The last outdoor sculptures realized by Moore before his death in 1986 are two related series: Bronze Form and Large Figure in a Shelter. A series of six and three editions respectively, they were cast and finished at Morris Singer Foundry outside of London in 1985. Some of the editions were not completed until after his death, as was the case with the fourth edition of Bronze Form, finished in 1987, purchased by the collectors Fran and Ray Stark in Los Angeles. The Getty acquired Bronze Form (1985, 4/6) as a gift from the Fran and Ray Revocable Trust in 2007, and it has since been prominently displayed within a reflecting pool adjacent to the Tram Arrival Plaza.

The Museum’s conservators have spent over a decade maintaining Bronze Form and planning for its long-term preservation. In 2010, a major treatment was carried out to remove an aged clear polyurethane coating which was replaced with an acrylic lacquer. By 2020, the condition of the bronze had changed enough to warrant a more extensive treatment. The surface developed uneven corrosion that blemished the golden patina.

Removing the corrosion would involve repolishing the surface and repatinating, which prompted more research on Moore’s original intent and expectations for the work in an outdoor setting. Even though his artistic process is well documented, the intent of the artist’s highly polished finishing for these later works is uncertain and a significant departure from his aesthetic norm. The following will review the evidence that supported the conservators’ final plan of action in the summer of 2022 to conserve Bronze Form.

Casting

The sculpture was cast in nine different sections using a bronze alloy containing tin, zinc, and lead and would have weighed approximately 1½ tons according to the foundry. Each part was sand cast, cleaned and bolted together, with a final connection of welding at the seams. After final assembly, the overall form would have been highly polished. From the very beginning, the overall tonality was not completely uniform. The welding metal joining the nine sections had a different alloy (significantly less zinc and lead) so the seams would have appeared more reddish. Additionally, due to segregation of the alloy during casting, the Getty’s Bronze Form developed large and fragmented lighter-colored surface blotches. X-ray fluorescence (XRF) analysis on the blotches revealed a different alloy to that of the bulk. The tin and lead levels in these areas are greatly enhanced (to approximately 14% and 7% respectively) and the zinc level is substantially reduced (to a little over 1%). It is interesting to note that these areas also show enhanced levels of silver and antimony impurities. This is probably of little physical consequence but may be attributable to the natural tendency of these elements to segregate with lead. This observation will be discussed further on, for it imposed a predicament to our treatment planning.

Patination

Polished bronze is reactive to air and will oxidize and change color without a protective coating. Moore often had the foundries apply chemicals to produce brown, green, or reddish colors – a finishing step called patination – ultimately followed by brushing on a protective wax coating. Some of his later works would remain golden, but even in those cases, a very light wash of dilute patinating chemicals would have been used, such as liver of sulfur or ferric nitrate. Moore often played with lights and darks with his patinas, but also loved how his static compositions would change as the natural sunlight cast additional highlights and shadows throughout the day. It takes a master to understand formulations, and to control the chemical mixtures with different means of application and heat. Moore’s assistants and foundry experts each had their own skilled (and often secretive) techniques. The applied patina converts the surface to copper oxides and minerals that continue to oxidize and react over time. Some of these products can be stable and even slightly protective to the bronze sculpture, while others (such as those from ferric nitrate), may be more unstable and unpredictable.

The Artist’s View

Moore understood the reactiveness of metal in an outdoor setting and wrote:

Bronze is a substance which is highly susceptible to atmospheric conditions. The chemical composition is largely determined by the climactic conditions in which the particular work is going to be set. Different things will happen to the patina of bronze according to the kind of atmosphere in which it is gradually weathered. My own patina is, of course, a preliminary to the one which nature will herself supply in time.

On the other hand, Moore also witnessed how less stable patinas could become unflattering and harmful to the bronze surface due to a variety of factors: poor maintenance, damages, harsh environments. Chief archivist at the Henry Moore Foundation, Michael Phipps, has said that in these cases, Moore would not oppose repatination and in some cases would advocate for reworking the surface.

Other Editions

The other five editions of Bronze Form “all had slightly different stories to tell,” according to extensive research by Katrina Posner, the Museum’s associate conservator in 2010, who “found it interesting that clearly due to the reactivity of the bright surfaces, these sculptures were all treated for the first time within a few years of their fabrication.” The second edition in Copenhagen, for example, was treated by the Moore Foundation by re-polishing the edges, and rewaxing. Over the years, the main body of the surface has darkened (assisted by sulfuric air coming from the natural sulfur springs in the area). The edition at the Kawamura Memorial Museum in Chiba (0/1) was restored by one of Moore’s assistants to remove a failed coating, re-polish the bronze, apply a potassium sulfide chemical patina, and spray a protective acrylic lacquer. In general, Posner found examples where the polished bronze appearance was either allowed to darken naturally, or via patination, or the surface was repolished to restore a foundry-made golden appearance and coated.

History of the Getty’s Bronze Form

When the Starks purchased Bronze Form, the sculpture was shipped directly from the foundry to their home in California. The bronze was damaged during travel and the surface was covered with handprints etched into the metal, corrosion from packing material, and marks from chemicals that dripped over the surface.

One of the foundry workers from Morris Singer, Reg Woolf, came to the Starks’ home and reportedly repolished the surface with an orbital sander, applied a liver of sulfur patina, and coated it with Incralac (acrylic) and wax. The details may either be incorrect, or another treatment followed without any known documentation, which was ascertained from surface and coating analysis done at the Getty revealing a clear polyurethane coating and no evidence of chemical patination. Other than a treatment in 2010 to renew the protective coating, the sculpture has been maintained by regular washing with soap and water and a yearly reapplication of a topcoat of wax.