EVALUATION OF CLEANING METHODS FOR THE EXTERIOR BRICK AT THE BROOKLYN HISTORICAL SOCIETY
CLAUDIA KAVENAGH, & GEORGE WHEELER
1. The first study was prepared by the Architectural Conservation Laboratory at the University of Pennsylvania in 1991–92. This research included a building history, terracotta characterization, mortar analysis, mock-ups using proposed repointing techniques, and limited laboratory and site cleaning tests. Integrated Conservation Resources Inc., a private firm with offices in New York City, undertook the second study, which concentrated on further exploration of cleaning methods.
2. A barrier coat of nitrocellulose glue was followed by a thicker coat of five-minute epoxy. The barrier coat was applied to prevent the migration of the five-minute epoxy, which is known to contain sulfur, into the brick.
3. In order to limit the test to the evaluation of the performance of only the exposed faces of the bricks, the sides of each sample were coated with Akemi Knife-Grade Buff. This coating formed a barrier to water so that uptake could occur only through the face of the brick. Cores measuring 82 mm in diameter were dried, weighed, and then partially submerged in water. The amount of water absorbed was measured by weighing the brick at set intervals. For comparison purposes, samples from five bricks were tested.
The authors wish to acknowledge the contributions of previous testing performed by the Architectural Conservation Laboratory and by Integrated Conservation Resources Inc., as well as project support provided by the Brooklyn Historical Society. Thanks to Richard Pieper and Dean Koga for their insights throughout the course of the project. Scanning electron microscopy was performed by James Martin of Orion Analytical. Graphic contributions were provided by Danius Glinskis, Annie Vatterott, and Beth Romizer of Building Conservation Associates Inc. On-site testing was performed by Richard Pounds of ArchaTechnology Ltd.
APPENDIX 1 INSTRUMENTAL ANALYSES
SEM-EDS generally was made using a Cambridge Stereoscan 100 scanning electron microscope coupled to a Tracor/Northern energy-dispersive spectrometer. Sample material generally was adhered to a carbon planchet or aluminum stub using conductive carbon tape, then coated with carbon or gold for analysis.
X-ray diffraction was performed using a Philips 1710 open architecture diffractometer. Samples were ground to fine powder in an agate mortar and pestle and adhered to a quartz plate. Instrument parameters are: 40 kV and 30 mA of copper radiation, 5–65 degrees of Bragg angle. Diffractograms are processed using Traces file manipulation software and phases identified with mPDSM search-match software.
X-ray fluorescence was performed on a Jordan Valley 3600 spectrometer. Analyses were performed nondestructively (i.e., without sample preparation) using 10 kV radiation from a rhodium tube and amperage to produce a dead time between 40% and 50%.
For FTIR, a Spectra-Tech IR Plan Research microscope was coupled to a Nicolet Magna 550 FTIR spectrometer. Both instruments were purged with dry air. Sample material generally was compressed onto a single Spectra-Tech diamond cell for analysis by transmission at 4 cm–1 resolution for 32–132 sample and background scans using Happs-Genzel apodization.
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SOURCES OF MATERIALSAkemi Knife-Grade Buff
Jaeger and Condino Inc. P.O. Box 592 35-44 61st St. Woodside, N.Y. 11377 (718) 335-8300Bac2Nu Stone & Masonry Cleaner/Restorer
Chemique Inc. 315 N. Washington Ave. Moorestown, N.J. 08057 (800) 225-4161Carbopol 940
B. F. Goodrich Specialty Polymers and Chemical Division 9911 Brecksville Rd. Cleveland, Ohio 44141-3247 (800) 331-1144Restoration Cleaner
PROSOCO Inc. 3741 Greenway Circle Lawrence, Kans. 66046 (800) 255-4255
CLAUDIA KAVENAGH received her M.S. in historic preservation from Columbia University's Graduate School of Architecture, Preservation, and Planning. She is director of the New York offices of Building Conservation Associates Inc., where her work combines the disciplines of historic preservation and materials conservation for the restoration of buildings and monuments. Address: Building Conservation Associates Inc., 158 West 27th St., New York, N.Y. 10001
GEORGE WHEELER is research chemist at the Sherman Fairchild Center for Objects Conservation at the Metropolitan Museum of Art. He holds a master's degree in art history from Hunter College of the City University of New York, a certificate in conservation from New York University's Conservation Center, and a Ph.D. in chemistry, also from New York University. His main area of research is the conservation of stone. Address: Metropolitan Museum of Art, 1000 Fifth Ave., New York, N.Y. 10028