Shoptalk—deciphering architectural and historic preservation jargon one word at a time!
prism glass tile
an architectural glass tile, typically about 4”x4” in size, that redirects natural daylight through reflection and refraction into a building
Prism glass tiles became popular after they were patented and first commercially produced by the Luxfer Prism Company starting in 1897. They were particularly popular in transom windows above storefronts along main streets with structure similar to a stained glass window using zinc came and lead solder joints to hold the glass tiles together.
Today, preservationists struggle to save these transoms. Prism glass tiles are no longer produced, making it difficult to properly restore missing tiles. Additionally, these transoms face a similar battle that many stained glass windows face. Without proper care and maintenance throughout the lifespan of an exterior leaded glass window, it can fall into extensive disrepair making restoration all the more difficult and quite pricey.
Want to learn more about prism glass? The Historic Prism Glass Companies of the United States is a fantastic resource outlining its many uses throughout the years. The National Park Service’s Preservation Tech Note on “Repair and Reproduction of Prismatic Glass Transoms” is also a great resource.
MJ Funk “New York Store” leaded prism glass clerestory discovered intact after over two decades of being covered during a recent condition assessment.
Close up of leaded prism glass discovered at the MJ Funk “New York Store” in Harrisonville, Missouri.