By Stephen J. Greenberg ~
Last month, on February 7, 2019, forty-five members of the Washington Conservation Guild (WCG) held their floating monthly meeting in the Rotunda and History of Medicine Reading Room at the National Library of Medicine. The Guild is a nonproﬁt organization of conservation professionals dedicated to preserving art and historic materials. Founded in 1967, WCG serves as a regional forum for its members. As their website states:
WCG is based in Washington, D.C., and draws its membership primarily from Washington, Maryland, and northern Virginia. Members represent a wide cross-section of the conservation community and allied professions. They work in government, state, and private museums, studios, and laboratories, and other cultural and academic institutions and organizations.
The Guild’s visit included a guided viewing of some of NLM’s oldest and rarest books led by its staff of rare book librarians, and presentations by three Guild members, two of whom are conservators at NLM, and whose work will already be familiar to regular readers of Circulating Now.
Holly Herro, NLM Senior Conservator, and Kristi Wright, NLM Contract Conservator, spoke about three ongoing conservation projects at NLM. The first is the ongoing research to fabricate an inexpensive anoxic frame for the Marshall Nirenberg DNA map. The frame is now fully operational, but the testing and monitoring of the frame goes on. In particular, Herro and Wright need to monitor the integrity of the O-ring seals, in order to ensure that proper levels of argon are maintained inside the frame.
Another topic covered by Herro and Wright was the now-completed encapsulation of the arsenic-laden pages of Shadows from the Walls of Death, the 19th century book of toxic wallpaper samples. Now that the encapsulation is completed, the book has been returned to the NLM stacks for examination and use by scholars and the just-curious. Shadows has become a favorite of the groups taking tours of NLM and of the History of Medicine Division Reading Room in particular.
The third project discussed by Herro and Wright is their newest. Working in conjunction with their counterparts at Penn State University and Smithsonian Institution Libraries, Herro and Wright are launching a new effort to better understand how the leather in historic bookbindings ages and deteriorates, and why modern binding leather, from the same species of animal but tanned, dyed, and prepared by modern methods, clearly ages differently and in many cases far less well than traditionally prepared leathers.
The preservation of binding leathers has always been a knotty problem. The exact species of leather (calf, sheep, goat, pigskin, vellum, parchment, even buckskin) is often difficult to determine, but each will need different conservation and storage. Moreover, modern leather simply doesn’t age well, and it is not clear why. The “Leather Discussion Group” will be using all of the modern technology at its disposal (DNA analysis of the leather, qualitative analysis of the modern and traditional chemicals used, even examining animal husbandry practices) to puzzle out the differences.
The third speaker was architectural conservator Justine P. Bello who discussed the effort of the National Park Service to clean the dome of the Thomas Jefferson Memorial of a particularly stubborn and mysterious grime that is disfiguring the famous building. Many theories have been advanced about the source of the discoloration: airplane exhaust fumes (the Memorial is on the approach path to Reagan National Airport), some sort of fungus, or just too much automobile traffic in downtown DC. Research show that the grime was in fact a biofilm with fungal, bacterial, and algal components. There were concerns that the biofilm was actually damaging the stone.
But how to clean it? Solvents, including even water-based cleaners and detergents, were out of the question, given the sensitive ecosystem of the Tidal Basin. Liquid residue would inevitably get into the surrounding waterways. Moreover, abrasives would certainly damage the stone. It was finally determined that a laser could be used to clean the stone. Lasers used no water or abrasives, they were gentle on both the environment and the building stone, and could be done a bit at a time. Finally, lasers left a natural-looking result—nothing was to look “too clean.” The majority of Bello’s presentation described the intricate choreography of the test cleaning of a selected area of the dome. The equipment was heavy, delicate, and the supporting scaffolding could NOT rest upon the historical building. But the test cleaning was a success, and the National Park Service is moving ahead to clean the entire memorial. The project is expected to be complete by May of 2020.
There do remain some unanswered questions, most importantly, will the biofilm come back after the cleaning. There are no answers yet, but Bello and her colleagues will be watching very, very carefully.
Photographs of the event by the author.