This Preservation Brief was developed under a cooperative agreement between the New York Landmarks Conservancy and the National Park Service. Mark A. Weber, Director, Technical Services Center, served as project coordinator for the Conservancy. The author, Martin E. Weaver, is the Director of the Center for Preservation Research at Columbia University. He is an internationally recognized expert in the conservation of architectural and cultural resources, a noted lecturer, and author of Conserving Buildings: A Guide to Techniques and Materials, as well as numerous articles on the subject.

Anne E. Grimmer, Senior Architectural Historian, Technical Preservation Services, Preservation Assistance Division, National Park Service, coordinated the development of this Preservation Brief and served as Technical Editor. Technical review of this publication by the following is gratefully acknowledged: Frances Gale, Training Coordinator, National Center for Preservation Technology and Training, National Park Service, Natchitoches, LA; Judith M. Jacob, Architectural Conservator, Building Conservation Branch, Northeast Cultural Resources Center, National Park Service, NY, NY; Andrea Mones-O'Hara, Regional Historic Preservation Officer, National Capital Region, General Services Administration, Washington, DC; Nicolas F. Veloz, Conservator of Outdoor Sculpture and Monuments, National Capital Area Office, National Park Service, Washington, DC; and Michael J. Auer, Timothy Buehner, Charles E. Fisher, and especially Kay D. Weeks, Preservation Assistance Division, National Park Service.

Washington, DC. October, 1995

This publication has been prepared pursuant to the National Historic Preservation Act of 1966, as amended, which directs the Secretary of the Interior to develop and make available information concerning historic properties. Technical Preservation Services (TPS), Heritage Preservation Services Division, National Park Service prepares standards, guidelines, and other educational materials on responsible historic preservation treatments for a broad public.