Allison Rabent is a pre-program volunteer at the Lunder Conservation Center. She is working with conservators on a variety of activities. Allison, along with the project's lead, Conservation Technician Susan Edwards, recently investigated an ongoing treatment of Hiram Powers' Greek Slave and shares their findings with us below. American Art's sculpture curator, Karen Lemmey, contributed to this post.
This is a full scale plaster cast of one of the 19th century's most famous and popular artworks, Hiram Powers' Greek Slave. In March 1843, Hiram Powers finished modeling the Greek Slave in clay and soon after his studio made a plaster mold and this plaster cast of the sculpture. The plaster cast was a tool that was used by the artist or a workshop to create a marble copy of Powers' original sculpture. The Greek Slave was one of this artist's most famous artworks and five marble replicas of this size still exist today. Along with this life-sized cast, American Art has a three-quarter marble version on display on the second floor of the museum. The cast has a series of metal studs, known as point marks, and graphite X's on its surface. Each of these points indicates a location of measure that would have been taken by a pointing tool. A pointing tool was a popular device for sculptors in the nineteenth century. It was used to take a series of measurements from a cast, such as this, that could be transferred to a block of marble. The tool would be moved hundreds of times from the fixed points on the plaster to the corresponding locations on the block of marble from which the replica was being carved. Each time, the tool would be used to measure location and depth on the marble block, thus creating a three dimensional guide for the carver. By chiseling along the measured guidelines, the marble carver could replicate the artist's original form with much greater ease and in much less time.
The Lunder Conservation Center is cleaning this plaster cast in anticipation of its display in the museum next summer. It will be the center piece for a discussion of Powers' work and the materials and methods used to create sculpture. Considering its age and its function in Powers' studio, the work is in good condition, and its treatment will only require cleaning of the surface. The conservators began with a light vacuuming in order to gently remove any loose dust and dirt. This was followed by a dry cleaning using vulcanized rubber sponges, which are suitable for the safe removal of particulate matter on dry surfaces, and especially useful for treating porous materials.
Extensive testing was done beforehand in order to determine the best method for cleaning, while facilitating the most control over the process. This was especially important because it is crucial that the small graphite X's covering the surface of the sculpture are not faded or removed during cleaning and that the evidence of the sculpture's purpose as a guide for the creation of the marble sculpture remains intact.
In order to complete the treatment, conservator, Hugh Shockey determined that a gel cleaning system would be the best course of action. This system was chosen because it allows for a cleaning mixture to be suspended on the surface without exposing the plaster to too much moisture. Once the gel is applied, it is lightly agitated with a brush around a small area. This action helps expedite the drawing of the dirt up from the plaster and into the gel. Once the area is cleaned, the gel is removed with dry swabs, and then any remaining residue is cleared with water.
Visitors can watch the Greek Slave being cleaned over the next few weeks on the fourth floor of the Lunder Conservation Center. In addition, American Art's sculpture curator, Karen Lemmey, will be writing a series of blog posts beginning in the spring of 2015, illuminating Hiram Powers' process and connecting it with contemporary 3D and computer graphics modeling processes.