This poster was presented at A Century of Design in the Parks Symposium, Santa Fe, New Mexico, June 21-23, 2016.
By Courtney Magill
This research focuses on the evaluation of the durability of traditional and modern sustainable hydrophobic and ultraviolet (UV) resistant treatments for historic log structures such as those found at the Bar BC Dude Ranch in Grand Teton National Park, Wyoming. These treatments were evaluated for their durability in accelerated and other weathering tests and their impact on aesthetic character. The testing was performed at The Architectural Conservation Laboratory (ACL) at the University of Pennsylvania in cooperation with the National Park Service and the Western Center for Historic Preservation (WCHP). Supplementary natural weathering is currently being conducted on site, initiated in summer 2015, in order to verify laboratory results and develop an environmentally-sensitive treatment protocol for local log structures that will aid in preserving original fabric while maintaining the intended age-value of the buildings.
Like many log structures in the American West, Grand Teton National Park’s historic structures are exposed to a large amount of UV radiation. In addition to problems arising from contact with water, the physical fabric of wood is damaged by UV light through degradation of lignin. Exposed wooden members are often affected in a matter of days. Small depth of penetration restricts damage to surface area; however, when combined with shrinkage and swelling of water sorption or abrasion from weathering, surface material delaminates, exposing untreated surfaces for further delignification. Additionally, coatings that do not protect against radiation also face polymer degradation from the release of free radicals in the wood caused by substrate surface breakdown.
Two traditional wood treatments, linseed oil and paraffin wax in mineral spirits, alongside five contemporary commercial products were selected for testing on several criteria. Ultraviolet protection was a paramount concern along with water repellency. Additionally, selected products were required to have little impact on the aesthetic appearance of the wood since coatings of regional log structures in the past were lightly colored. Low VOC content was also considered due to increasingly strict laws on volatile organic compounds.
Accelerated weathering was conducted using a QUV Weatherometer at the ACL which simulates weathering by subjecting samples to cycles of UV-B light, heat, condensation, and sprayed water. While artificial weathering occurs in more intense, concentrated cycles than those in nature, results can be a good comparative indicator of longer-term performance of selected treatments. Products were tested on samples of local lodge pole pine (Pinus contorta latifola), a common building material in the area. Samples were evaluated and monitored for weight, surface, and color changes to observe surface degradation throughout the weathering process. Comparison of treated samples pre- and post-weathering led to judgment on continued field testing of the products. In summer of 2015, a weathering rack was assembled and placed in Jackson Hole in order to observe long term natural weathering of samples of pine treated with those products deemed viable after accelerated weathering testing. The combined results of the lab and field testing programs will inform the Park’s conservation and maintenance program for the many historic log structures in their care.
Courtney Magill graduated from the University of Georgia with dual Bachelor of Arts degrees in art history and classical culture in 2011. She continued her research in art conservation through an internship with the Curator of Decorative Arts at the Georgia Museum of Art and an apprenticeship with a private conservator in the Athens, GA area. In the summer of 2012 she attended the Museum of Early Southern Decorative Arts’ Summer Institute, concentrating on the decorative arts of the southern backcountry and an AIC workshop located on Ossabaw Island, GA in 2013, learning preventative preservation tactics through implementation in the Torrey Mansion. Courtney recently completed her Master of Science in Historic Preservation at the University of Pennsylvania in May of 2015 and received The Anthony Nicholas Brady Garvan Award for an Outstanding Thesis. Her coursework has concentrated on the theoretical, logistical, and physical approach to the conservation and preservation of historic buildings and sites, and has focused on conservation as it applies to building materials. Her thesis explored performance testing of hydrophobic and UV resistant protective treatments for the exteriors of historic log structures, and she continued her research in the summer of 2015 by constructing a natural weathering bracket on-site in Grand Teton National Park to provide real-time weathering results for these treatments. Courtney recently presented this research at the APT Conference in Kansas City and will also present it at the AIC Meeting in Montreal this May. She is currently continuing as lab manager for the Architectural Conservation Laboratory and a post-graduate fellow at the University of Pennsylvania.