AIC's 47th Annual Meeting

This presentation will combine historic research into cast stone companies of the Northeast United States and Canada, and discuss their materials and practices, including how they marketed their material, as well as consider the conditions and analysis, conservation, and preservation issues of several examples. Cast stone is a highly refined form of concrete that is pressed into molds to simulate natural stone. Cast stone can be molded to represent plain ashlar blocks or intricately carved ornament. The basic mixtures are composed of water, fine and coarse aggregate, cementing agents, and pigments. Cementing agents can include lime, natural cement, portland cement, oxychloride, and sodium silicate. After casting and curing, manufacturers would typically tool, abrade, or acid wash the surface to remove the cement layer and create the desired finish. Not only can this material be found in a variety of applications, because each manufacturer had their own secret recipes and often imported their ingredients. Early cast stone operations imported their natural and portland cements, until domestic portland cement production increased and prices dropped. As this occurred, the industry developed, and by the mid twentieth century numerous patents had been filed for cast tone formulations and finishes. The boom of the cast stone industry predates standardization, such as ISO and ASTM. As a result the condition of cast stone can vary by manufacturer and even building to building depending on the year of construction. Information isn’t always readily available on each cast stone manufacturer, but with an ever-growing body of historic materials sometimes you get lucky. When luck isn’t on your side, science is. Petrographic analysis of cast stone is integral in understanding its condition and deterioration. Lastly, this presentation will discuss how cast stone is very much alive in the building industry, and will look at how the material use has changed over time and what that means for its preservation and conservation in the future.