Present: Robert Adam, Jack Alvarez, Neal Boornazian, Matthew Bronski, Cynthia Chabot, Rob Davidson, Gus Fraser, Jack Glassman, Sarah Gray, Patrick Gutherie, Jean Marie Hall, Marie Helms, Julie Klump, Chris McNamara, Laura MacKowiak, Henry Moss, Ivan Myjer, Deborah Robinson, Lance Robson, Brian Roche, Susan Schur, Irving Slavid, Malcolm Smiley, Kim Sykes, Robert Thomas, Erin Tobin, Eric Ward, Norman Weiss, Sara Wermiel 1. Conservation Forum- Masonry Conservation, The Development of New Products: a. Jean Marie Hall, Project Manager at Integrated Conservation Resources (ICR) explained why historic burial grounds are such fruitful study sites for the weathering and deterioration of masonry. Stones are dated, easily reachable, and pretty much there in perpetuity. We know when they were erected and often where the stone came from. Furthermore, the records for individual sites often track major repairs and provide an usually reach basis for longitudinal comparison of different stones' resistance to moisture, chemical attack (fertilizer, acid rain), and conservation treatments (hot waxes, epoxies, various cleaners and consolidants). The stones' condition is less complicated by associated architectural and structural detailing. With fewer variables, it is often simpler to link causes and effects. b. Norman Weiss, Senior Scientist at ICR and partner of Monument Conservation Collaborative Materials (MCCM) identified key episodes in a 115 year long sine wave of ingenuity, confidence and, often, disillusion as successive approaches to waterproofing and patching were tracked through time. Farnham Wax was an external molten wax application that remained in use from 1885 into the 1940's. Glidden Paint introduced a product called Dri-wall through one of its subsidiaries that held center stage for a decade in the Fifties and Sixties. c. In 1969, Norman began his work in historic cemeteries in Massachusetts, beginning in Gloucester. He later turned his attention to the treatment of stones in the churchyards of Cambridge and Boston, and subsequently to Trinity Church on Wall Street in New York City with silane-modified hexasilicates. (State law required experiments on grave markers in Massachusetts to be authorized by all living descendents of the interred!) In 1976, Norman Weiss with other researchers began testing the effectiveness of epoxies on slate and has now accumulated a quarter-century record of comparative slides of individual stones. Many patching materials are often mechanically successful but drift in hue and tone over time. Norman pointed out the contribution to Boston's Historic Burying Ground initiative that began about 1985 where treatments have been carefully recorded, MSDS sheets kept, and dates of application kept together. Obviously, these records are specific to Boston's climatic situation. A further visual resource resides in photographic collections of gravestone art. Photographers Farber and Rigby have gravestone images that span decades at the Museum of Fine Arts. Jean Marie Hall, Ivan Myjer of Building and Monuments Conservation, Gus Fraser of Mount Auburn Cemetery and other active members of the Boston area's Conservation Forum have begun to collect longitudinal field information that is not driven by marketing and not limited to the conditions of testing laboratories, then return conclusions about effectiveness to specifiers and product manufacturers. d. Norman described the testing and introduction of Conservare HCT (Hydroxoxylating Conversion Treatment), a new penetrating pre-consolidant that has come from research and development investment by Monument Conservation Collaborative Materials (MCCM), with manufacturing and distribution connections to ProSoCo. In 1996, Norman and Irving Slavid started research leading to about 75 formulations of a new pre-consolidant that were narrowed to the most practical. The waterbourne treatment reacts with individual calcium ions in the surface of the stone and produces an interstitial matrix with connection at all grain boundaries. The material is water repellent and relatively insensitive to acidity. An advantage of HCT is that it can also attach ethyl silicates that were previously not useable on limestone or marble. The material is safe in solution with potable water. Cure time is 48 hours. ProSoCo's lab in Kansas is continuing tests on acid resistance and mechanical consolidation. HCT is meant to help current stone conservation treatments work more effectively on carbonate building stones. Product information and Material Safety Data Sheets are available from ProSoCo. Norman noted that there is more field testing in the United Kingdom now than in the United States, although English Heritage has limited the test sites to "hopelessly deteriorated" cases, which may not provide useful comparisons for those cases where decorative stone is intact enough for us to want to consolidate and keep it rather than insert recarved dutchmen. The UK trials do involve two kinds of limestone. e. Ivan Myjer presented examples of problems from the Bowdoin Street face of the 1888 Massachusetts State House addition and at the Appellate Courthouse building in New York City, where Daniel Chester French statuary eroded so badly that around 1985, new replacement carved faces were attached. Ivan's presentation focused on the specifiers' risk in specifying new products to address loss of detail and granulation at various depths in the stone. Testing on the Appellate Courthouse was done by the NYC office of Building Conservation Associates with Dr. George Wheeler and Norman Weiss. Ivan was the conservator for the design team on that project reviewing test data and recommending final treatment. Ivan cited cross-sectional studies done by Dr. Sewitz in Rome showing 5/8" depths of granulation in friable Italian marble, whereas depths of incompetent stone may be 3" in buildings on the East Coast of the United States. Ivan noted that the Massachusetts State House specifications were prepared by Dr. Judy Selwyn and Goody/Clancy before HCT became available, but more to the point, tests on the 2 1/2" deep deterioration on the acanthus leaves on the Corinthian column capitals indicated that HCT would not be an effective treatment. So far, there have not been field trials in the United States that allow a good comparison to ProSoCo's Conservare HO. At the Appellate Courthouse damage to the articulated stone surfaces is not as deep. f. This application of intellectual voltage from the New England Conservation Forum to the BSA's Historic Resources Committee sparked equal parts of admiration for the research and development and open exchange of ideas and field results to conservative belief in recarving and Dutchmen in the face of deep granulation and the lack of long term testing in situ. Norman and Irving of MCCM, along with other masonry conservators gave a wonderful comparison between the diagnostic "touch" of at an experienced mason's fingertips and the mechanized tests for abrasion (Taber abraser tests for stair treads) and microabrasion. Arcane as these observations may seem, increasing the sophistication of testing is necessary to build understanding of the limits of new products and confidence about when to specify them. Currently, there are no ASTM standards for microabrasion resistance that relates sensibly to problems like the deterioration of French's carved faces at the Appellate Court. Look for an upcoming issue of the journal of the American Institute of Conservators (AIC) where this problem will be examined in detail. Meanwhile, HCT may constitute a significant new addition to the battery of surface treatments for relatively sound and intact carved limestone, travertine and marble that can slow the rate of deterioration.
Future BSA Historic Resources Committee Meetings: The next meeting will feature Catherine Truman talking about war-torn Mostar. Read the appropriate Ivor Andric stories by way of preparation. In March, Gary Hilderbrand will speak about the Irwin Miller Garden and the preservation of historic landscapes.
8: 00 a.m., Thursday, February 14, 2002 Focus Topic: Catherine Truman on Mostar (Look for her exhibition on Mostar at the BSA in March.) The Architects' Building, 52 Broad Street, Fifth Floor, Boston |