On August 5 and 6, two representatives from Bruker Corporation visited the Cantor Conservation Lab for a hands-on workshop on the fundamentals of X-ray fluorescence spectroscopy (XRF), an elemental analysis technique. The workshop was open to researchers from Stanford, as well as from local museums. Although our group was small, it represented a diverse selection of interests and backgrounds, including archaeology, geology, chemical engineering, materials science, and art conservation, indicating the wealth of applications for XRF.
The workshop was divided into two sessions. The first day explored the theory and technology behind XRF, while the second day focused on the analysis software and calibration process. The specific model we used was a brand-new Tracer III-SD, lent to us by Bruker. After being reassured that the levels of radiation emitted are minimal, we tested the Tracer on a few objects we had brought to the Conservation Lab, including an ancient Chinese bronze dagger and Flowers in a Glass Vase by Ambrosius Bosschaert the Elder.
Because the museum is closed to visitors on Tuesdays, we also had the privilege of using the Tracer up in the gallery. Of special interest to me was a brief investigation that we conducted on a bronze statue of a Daoist deity. To the naked eye, it appears as though the surface of the statue might contain some traces of gold, particularly on the robes of the deity. The Tracer was able to not only confirm this, but also identify mercury, which is expected because these two elements easily amalgamate.
Like any analysis technique, XRF has certain limitations. For example, it cannot detect elements lighter than neon, and the results can be difficult to quantify. Nevertheless, the fact that the instrument is both portable and nondestructive makes it highly valuable to the art community. I look forward to gaining more experience with the Tracer for my own project on a Shang dynasty bronze vessel, and I believe the Conservation Lab will find many uses for it.
Mark Di Suvero’s The Sieve of Eratosthenes was added to the university’s outdoor art collection in 2000 by Daniel Shapiro and Agnes Gund. It was originally sited on the north side of the Cantor Arts Center and was recently moved near the intersection of Escondido and Galvez Mall by Meyer Library.
The new location puts The Sieve of Eratosthenes in greater student traffic. The sculpture invites viewers to experience its form from all sides and even underneath. This does not, however, condone the following:
In spite of the sculpture’s powerful forms and seeming imperviousness of its I-beams, the sculpture is still susceptible to degradation. In addition to looking fantastic, the paint and primer layers protect the underlying steel from corrosion. When vandalism occurs to the paint surface, the steel is exposed to the environment and leads to rust.
The outdoor sculpture team works hard all year long to care for Stanford’s sculptures, so do your part! If you are trying to get your work done or “play” around the sculpture, try also to take a few minutes to contemplate the beauty of its forms and how this reflects Di Suvero’s perception of reality. Think about the enormity of the feat that brought such a massive object into existence. Let this object inspire whatever non-vandalizing activity you are engaged in!
Auguste Rodin’s The Three Shades (created 1881-1886, cast 1979-80) is currently on view at in the Rodin Sculpture Garden just off Lomita Drive. The sculpture’s location, pose, scale, and low platform make it particularly vulnerable to visitor damage. Recently, the patina on the base of The Three Shades was extremely abraded. Note the bright golden color of the metal showing through!
(above) The dark brown patina was worn away by visitors standing on the bronze base, probably due to a tempting photo opp.
Wax is an important protective layer for bronze, as it slows down corrosion and serves as a barrier from abrasion, graffiti, and other undesirable occurrences. The Stanford outdoor sculpture conservator and maintenance crew spend much of their time maintaining the coatings on the University’s collection. The wax coating on the base of The Three Shades was painstakingly rebuilt over several days.
(above) Several layers of a pigmented microcrystalline wax were added to the base and buffed afterwards.
So please, don’t step on the art!
author, Lauren Sweet
This past month The Burghers of Calais have been kept under wraps. No, they haven’t been shrouded in secrecy, they’ve been swaddled in blankets. The Burghers of Calais, one of Auguste Rodin’s most famous collection of statues and among the premier pieces in the Stanford collection, have been in preventative protection during a nearby drainage-modification project (the old system was causing pooling).
The Outdoor Sculpture Conservation Crew first washed the statues using a mild detergent called Orvus, then rinsed and dried the bronzes with lint-free rags. The state of the protective wax coating was assessed, and the six bronze men were wrapped in heavy duty blankets (more about this process here…). Once the construction was complete, the statues were unwrapped, safe, sound, and ready to pose with their many visitors.
Authors: Lauren Sweet, Bryce Cronkite-Ratcliff, Elizabeth Saetta
Rodin’s The Gates of Hell is one of the crowning jewels of Stanford’s sculpture collection. A monumental work of this scale requires a significant conservation effort. As with all sculptures in the outdoor sculpture collection, The Gates is cared for by the conservation crew, and its condition is constantly monitored. All bronze sculptures receive an annual treatment of washing, waxing, buffing, and any other additional conservation treatment necessary, including touch-ups. This conservation work preserves the sculpture in perpetuity and heightens visitors’ experiences of it.
The Treatment: August 5th through 9th 2013
Preventative conservation treatment of The Gates of Hell is a weeklong project.The work began early on a Monday morning with a thorough washing of The Gates. The conservation crew faced many challenges: first, how to reach and wash the upper reaches of a massive sculpture nearly 20 feet tall. A 45-foot electric boom lift with an articulated arm was the answer, but this posed its own challenges, including how to maneuver the lift into a garden full of other priceless Rodin works, and how to position it in relation to the large, broad, raised pedestal that The Gates sits upon so that the arm of the lift could extend to reach the entirety of the sculpture. In areas where the lift arm could not reach, a large ladder was used.
Once these logistics were smoothed out, the cleaning could begin. An entire day was dedicated to washing The Gates. Every crevice of the sculpture had to be rinsed, washed with soft nylon brushes and a gentle detergent known as Orvus, rinsed again, and then dried. All of these steps are crucial. The first rinse helps to remove large debris or dirt accumulations on the sculpture. Interesting things were found at this stage, including several small rocks high up in the top pockets of the sculpture and a headband that must have been slung onto the roof of the piece. Soap and soft scrub brushes do what one would expect, assisting in the removal of the tougher grime, including things like bird droppings. Another unexpected discovery during the treatment was four individual wasp nests, nestled in among the twisting figures in low relief areas. Professional exterminators were called in to remove the nests so that conservation could proceed. After the final rinse, the sculpture was dried with soft towels to prevent minerals in the water from depositing on the surface through evaporation. These mineral deposits detract from the sculpture’s patina and are difficult to remove.
The next steps were wax application and buffing. The wax application is ideally done when the metal is warm, so that the wax melts and then coats the metal surface thoroughly and evenly. To get the most complete and successful application, propane torches were used in conjunction with the heat of the afternoon sun. The conservator’s tool kit included: a tinted micro-crystalline wax thinned with mineral spirits, brushes, propane torches, and nylon stockings. Once the wax was applied, the spirits evaporated, leaving only the protective, hard, solid wax layer behind. At this point the surface was thoroughly buffed, a job for which the soft, fine nylon of women’s tights is perfect. Buffing smoothes brush strokes and irregularities in the wax application, and the resulting shine reveals the detailed dimension and relief of the sculpture.
By the end of a long week, the conservation crew had washed and waxed not only The Gates of Hell, but also the statues of Adam and Eve that flank The Gates, and The Spirit of Eternal Repose that sits high atop a column nearby. The result is a cleaned, beautifully shining bronze—shielded from the elements with a protective coating so that these masterpieces may be enjoyed by generations of visitors.