Glass has been made in many forms for about 4500 years, but the first "glass window" (as we would describe them today) was likely created during the Roman Era. "Broadsheet glass" as it is called by historians today, was manufactured by blowing an elongated balloon of glass, and cutting the ends off to create a glass cylinder. The cylinder was split, unrolled, and flattened on a hot iron surface to create flat sheets of glass. This method produced small, cloudy plates that were leaded together to create large-scale windows or placed into wooden frames to let light into buildings.
|Artisan making crown glass; image credit|
By the 17th century, window production methods in Europe and the US Colonies changed to blown glass plates. An artist would blow molten glass into a balloon, cut the end opposite the blowing rod, and spin the glass to create a large, flat, and round window. This type of glass was called "crown glass" and it allowed for the creation of larger windows. Crown glass could be installed as a larger window or cut into smaller rectangular lights.
|Interior view, detail of transom to highlight crown glass, with scale - Graeme Park, 859 County Line Road, Horsham, Montgomery County, PA HABS PA, 46-HORM; Jack Boucher [Public domain], via Wikimedia Commons|
As the technology for creating larger panes of glass became easier, demands for larger windows increased and architectural designs pushed the limits of what glass artisans could do. The Federal Style of architecture, the popular style of time, utilized the larger panes of glass to create fanlights and Palladian windows.
|Interior view, first floor, center room, view to door with fanlight above, with scale - |
National Park Seminary , Colonial House, 2745 Dewitt Circle , Silver Spring,
Montgomery HABS MD, 16- SILSPR, 2L-17; Jack Boucher [Public domain], via Wikimedia Commons
By the turn of the 20th century, laminated glass soon followed, which allowed for two panes of glass to be stacked together with a thin plastic sheet in between making the glass less susceptible to breaking. And, in the early 1950s the creation of float glass by Sir Alastair Pilkington in England became the preferred method of glass manufacturing. Float glass manufacturing fires glass at temperatures over 1000 degrees Celsius and floats ribbons of glass over molten tin spreading it thin and cooling it slowly to the desired thickness and size.
By the mid 20th century, glass manufacturers could produce glass panes the size of walls which again changed the architectural landscape. Modern architecture of the 1950s and 1960s utilized the huge panes of glass to open up spaces within the home to the outside world. Finished in 1951, the Farnsworth House of Plano, Illinois designed by Ludwig Mies Van der Rohe demonstrates the open concept and capabilities of modern glass manufacturing.
|Farnsworth House. Carol M. Highsmith [Public domain], via Wikimedia Commons|
Today, float glass can be produced as thin as 0.4 mm and glass can be produced in any number of colors, textures, and sizes.