During the late 1920s, the Bell Asbestos Mines operating in Québec, Canada were supplying asbestos for the building trade. Dixie Asbestos Company of Birmingham, Alabama served as the southeastern distributor for Ambler Sound Absorbing Plaster, which had been developed in 1924 by the Bell Asbestos Mine's Pennsylvania owner Keasbey & Mattison. The Massachusetts Institute of Technology tested the new plaster product and claimed that as applied by a Boston contractor, it could absorb up to 35% of the sound that struck it, depending on the pitch. Keasbey & Mattison recommended applying the plaster as a finishing coat (over gypsum plaster, lime and sand plaster or over concrete) 1/4" thick. The company also recommended cutting off all air circulation during the drying process so that it would dry uniformly. Advertising to architects, the company advised: "Send plans, including data on interior surfaces and furnishing, to our nearest branch office and prompt analyses and recommendations for your requirements will be given without obligation to you. In this way, correct acoustics may be predetermined before final working drawings are completed."
If you want to read a portion of Manfred Schroeder's Distinguished Lecture on "Reverberation: Theory and Measurement" that was delivered during the Wallace Clement Sabine Symposium (1994) at MIT, click here.
Image: Bell Asbestos Mines, Inc. Thetford Mines, P.Q., Canada. [p. 12] A.I.A. File 39--A and B. "Ambler Sound Absorbing Plaster." Ambler, PA: Keasbey & Mattison, c. 1928. Architectural Trade Catalogs Collection, Southeastern Architectural Archive, Special Collections Division, Tulane University Libraries.
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