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The Schenectady, New York, City Hall was designed by McKim, Mead, and White, Architects and constructed in 1930–1931. In recent years, severe deterioration of the exterior marble architectural elements was observed by city officials. As a result of this concern, a study was undertaken to analyze the causes and extent of deterioration, as well as methods for its arrest and control.
Investigation of the marble deterioration was carried out using the following equipment and techniques:
(a) optical microscope with photomicrographic dispersive staining capability,
(b) scanning electron microscope and computer-based energy-dispersive X-ray microanalyzer,
(c) ion chromatography,
(d) electron microprobe, and
(e) environmental pollutants data.
Based on this analysis, the following conclusions were drawn regarding the deterioration of the marble:
1. The deterioration of the marble is caused by a constant direct chemical attack by sulfuric acid. 2. Nitric acid has not played a major role in the deterioration of this marble. 3. Acid precipitations have not played a major role in the deterioration of the marble. 4. The major vehicle for attacking the marble is sulfuric acid produced continuously on wet surfaces by the heterogeneous oxidation of absorbed sulfur dioxide (SO2) in the presence of catalysts associated with the burning of fossil fuels.
As the result of these investigations, a major program for the cleaning and conservation of both the exterior and interior marble was prepared and put into effect. It consisted of the following actions:
(a) thorough cleaning of the exterior marble to remove gypsum crusts and sulfur using low-pressure water washing with the use of chemical cleaning agents in areas with severe deterioration, (b) cleaning of the interior marble using liquid cleaning agents and poultices, and (c) preparation of a long-term building conservation/maintenance/repair program for the City Hall to arrest future deterioration.
marble deterioration, marble cleaning, marble conservation/stabilization, marble deterioration analysis, scanning electron microscope, computer-based energydispersive, X-ray microanalyzer, ion chromatography, electron microprobe, atmospheric pollutants, sulfur dioxide oxidation, sulfuric acid, gypsum crust removal, restoration mortar repairs, heterogeneous oxidation, masonry, masonry cleaning
Partner, Mendel · Mesick · Cohen · Waite · Hall Architects, Albany, NY
Research associate and project director, Atmospheric Sciences Research Center, State University of New York, Albany, NY