The Materials Conservation Program works to bridge the gap between laboratory science and real- world historic preservation applications.
ADVANCING 3D TECHNOLOGIES
NCPTT explored the latest in digitization technologies for cultural heritage through the 3D Digital Documentation Summit held at the Presidio, San Francisco, July 10-12, 2012. The summit was jointly organized by the National Center and the NPS Intermountain Regional Office, and hosted by the Presidio Trust. Topics at the summit ranged from the integration of digitization and 3D scanning with traditional hand measuring techniques at World Heritage Sites to the classification of photographic paper texture using photographic techniques. The summit concluded with an open discussion about ways to advance this technology for the preservation of cultural heritage. Many of the presentations were videotaped and highlights are available on NCPTT’s website.
In addition to lectures and panel discussions, the third day of the summit featured four hands-on demonstrations. CyArk exhibited their mobile application for presenting point cloud information on monuments of historic significance, such as Mount Rushmore. Cultural Heritage Imaging (CHI) demonstrated the use of Reflectance Transformation Imaging to gather 3D information on cultural objects. Leica Geosysytems demonstrated their Scanstation C10 laser scanner in a mock scanning of the summit venue. The Center for Digital Archeology and the Presidio Trust provided a tour of the De Anza Room of the Presidio Officers Club, showing how a variety of documentation tools, such as gigapan photogrammetry, were integrated and utilized in the restoration of the building.
Many of the eighty-eight participants noted that they appreciated the opportunity to meet experts working in different areas of 3D documentation. NCPTT is exploring ways to continue the conversations started between experts at the summit and expand the discussion to a larger audience.
CONVENING EXPERTS IN FOLK ART CONSERVATION
The National Center continues to be a leader in convening experts to address unique conservation programs. In February, it focused on the conservation of under-appreciated works by non-traditional artists, including outsider and folk artists. Works of art made by untaught artists tend to be made of a wide variety of materials that are not commonly found in museum collections. In addition, the works are not widely accepted within some circles of the art world and may therefore have less care and attention paid to their preservation. NCPTT’s Divine Disorder, Conserving the Chaos conference was held in February on the campus of Northwestern University in Natchitoches, Louisiana. The program featured two days of contributed papers with topics ranging from identification of forgeries to site stabilization of large-scale steel whirligigs. The talks were “live-streamed” and recorded, and the archived footage has been made available on NCPTT’s website.
In addition to the scheduled lectures, an opening reception was held at Melrose Plantation to highlight the murals and works of Clementine Hunter. The conference featured a gallery show of Hunter’s original works, mirrored by William Toye forgeries. Presentations were made by Friends of NCPTT President Tom Whitehead and the FBI agent who managed the Clementine Hunter forgeries case. NCPTT’s labs hosted several evidence gathering sessions with the FBI, US Attorneys, and art microscopy experts from the McCrone Research Institute that led to the convictions of the forgers and those responsible.
STUDYING THE PERFORMANCE OF PRIMERS
One way of protecting historic wooden structures is to keep them well painted. This summer, intern Laura Lee Worrell began a study on the performance of primers to help homeowners select the best paint system for their historic properties. Primer serves as an undercoat to help bind paint to its substrate. In this study, Worrell tested three different paint systems on untreated weathered wood similar to that found in historic structures. Samples were treated in five different ways using a mixture of paint and primer systems.
Samples were characterized by color, gloss, surface smoothness, and weight before and after accelerated weathering. In addition to laboratory tests, Worrell conducted a survey to obtain public opinion on the visual quality of the weathered paints. Work is on-going through a joint venture with the College of William and Mary’s Surface Characterization Lab. However, according to the opinion survey, Zinsser one-coat oil-based primer with an additional two coats of latex paint maintained the best visual appearance after weathering. A full report is forthcoming.
CONTINUING RESEARCH ON REMOVAL OF CRUDE OIL
As a result of NCPTT’s participation in the multi-agency task force responding to the BP Deepwater Oil Spill, Materials Conservation staff have undertaken several research projects to determine the best methods for removing crude oil from cultural materials. These materials included archaeological shell and bone, historic brick, and most recently, stone (limestone, marble, and granite).
Researchers collected samples of crude oil from Fort Livingston, a Third System fortification located on Grand Terre Island off the coast of Louisiana. The oil was then applied to samples of limestone, marble, and granite and artificially weathered. Researchers tested the effectiveness of two cleaning products that performed well in the field and in other lab studies. Cleaning methods included those recommended by the manufacturer as well as applying the cleaner in a poultice. Samples were evaluated using color measurements, contact angle measurements and UVA fluorescence. The investigation showed that some oil remained on all cleaned samples. Poultice applications were more successful in removing oil from the surface of stones and did not mobilize oil to penetrate further into the pores of the stone.