This is a guest post written by Objects Conservator Liz Peirce. She is responsible for the care and treatment of the Library’s collection of 3D material, ranging from cuneiform tablets to modern plastics.
While we discussed previously the removal of an unexpected resident from one of these models, here we will focus on the conservation treatment of two large scale architectural models within the Library of Congress’s collection. We will also be discussing the treatment in more depth with more images during the upcoming Preservation Week!
The Library holds several architectural models, including two large-scale architectural models that were selected as part of a larger loan to the Metropolitan Museum of Art, scheduled for September 2024. The models are of two buildings by Paul Rudolph that were never constructed – the Sino Tower, Hong Kong, and the Graphic Arts Center, New York City. In 2001, the Library acquired Rudolph’s archive, and until March 2023 the models were stored in their original shipping crates in off-site storage facilities; being too large and in too poor condition to be kept on the Library’s main campus on Capitol Hill.
Architectural models are not generally intended to survive for several decades, and are constructed in a way that focuses on the visual qualities over the structural stability. For example, the Graphic Arts Center model is constructed of four modules that slide over a central light tower. These modules rest on two pins each, and the pins are not fixed in place. With sufficient rocking or vibration, the pins are free to shift out of position, allowing the modules to drop onto each other and causing significant damage and collapse.
The Sino Tower model, despite looking very solid, is only held in place with two bolts. There is no continuous support through all the layers – each floor is glued to the next, with most of the stability coming from the plastic struts in the dividing floors. Many of these joints were loose, detached, or missing completely. Several pieces had fallen from each model and were found lying on the interior crate supports. This instability increased the fragility of the pieces – as more elements became detached or loose, more stress was put on the remaining elements, increasing the chance of damage or loss.
Beyond the structural issues, both models were covered with a thick layer of dust. At some point, both models had been exposed to a water event which drove the dirt into the unvarnished wood surface, causing the layer to cement and stain, as well as causing tidelines. On the Graphic Arts Center model, this wet dirt then splattered onto the plastic windows, creating a speckled grime on the otherwise clear surface. The water did more than just stain, however. The thin cut wood absorbed the water and curled, causing walls to peel away from their ceilings, plastic windows to detach from their walls, and for walkways and bridges to distort. Needless to say, any conservation treatment was going to be a daunting challenge.
After an initial visit to our off-site location to examine the two models in person and take notes on condition, a treatment estimate was put together. The models would need extensive cleaning, flattening and consolidation of lifting wooden elements, location and reattachment of original detached pieces, recreation of missing elements, and stain reduction of tide lines caused by the water event. Overall, it was estimated that the treatment would take 496 hours to complete. While it is not unusual for conservation treatments to take several months, or even years, these models were slated for catalog photography in December 2023. Because of the short timeline, and the extensive work to be completed, more hands were needed. Seizing the opportunity to expand the experience and knowledge of the Collections Conservation Section Technicians, all five technicians were involved in the treatment of the large Graphic Arts Center.
With a treatment plan in place, the models needed to be prepped for shipment to Capitol Hill. Detached pieces from each model were labelled, collected, and placed in custom boxes for shipment. Due to the fragile construction of the Graphic Arts Center model and the insufficient support provided by the crate, we decided to disassemble the model and pack each module into its own custom box. Each module and the base were labeled with a tag on the same corner to help with orientation for assembly later.
Once in the lab, the first step was to remove the extensive dust and grime from the surface. The first two passes were completed using a soft brush and a variable-speed vacuum fitted with micro-attachments. Removing this loose layer of dirt was essential to prevent driving more dust into the wood. Once vacuuming was complete, the surface was cleaned using soot sponge and Groomstick. Soot sponge is a vulcanized rubber sponge that is used to remove soot and smoke damage from materials after a fire, and works by “grabbing” small electrostatically charged particles to remove them from the surface, while Groomstick is kneadable and lightly tacky, which makes it easy to mold around the end of a skewer to reach narrow spaces.
The acrylic windows and metal wires were then cleaned using deionized water on cotton swabs. Plastics, in particular, are very susceptible to damage from abrasion, so care was taken to prevent scratching these surfaces. While water was initially very damaging to the wood on the model, when used in a controlled way it can help flatten lifting edges. Humidification packets were created to help soften the wood, allowing for the pieces to be gently reoriented to their correct positions and glued in place. When there were particularly large gaps where the wood would not be held in place with gentle pressure, toned Japanese tissue twists were used to bridge the gap between the wall and ceiling or floor.
Once clean, elements that had broken off over time were reattached to the model. Much thought went into the selection of an appropriate adhesive – most solvents and adhesives that are commonly used in objects conservation have the same solubility as the acrylic of the windows. This would mean that the joint could not safely be removed in the future without causing more damage. However, water-based adhesives have low adhesion to the plastic surface because of the high surface tension. To circumvent this, a thick methylcellulose gel was used – it has the advantage of being safe to use on the plastic surface, is readily reversible, and the thickness of the gel helps create more of a physical bond between the plastic and wood. After reattaching all the detached pieces, anything that was missing was then recreated and attached to help complete the piece. Balsa wood of various thicknesses was dyed to blend with the aged wood, replacement acrylic windows were cut from Vivak, replacement support pins were made from brass wire, and a missing wire was made of brass wire wrapped in toned Japanese tissue. For the Sino Tower, moss caps were made to recreate the missing foliage on the trees.
The final step was to reduce the tidelines on the wood from the water event. Several tests were performed to see what had the best results for reducing the staining. We chose Agarose gels in deionized water, as it was the most successful at reducing the stains without blanching the wood beneath.
After 495 hours total treatment time, just one hour less than originally expected, the models were completed!
It takes many people to make something this complex come together. Many thanks to Anna Zastrow, Annie Immediata, Chloe Genter, Mary Elizabeth Watson, Paul Asta, Ken Grant, Mari Nakahara, Aliza Leventhal, Rachel Waldron and Marcus Toler!
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