Window Glass

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Art

Flat glass has virtually no artistic value in its own right, however, arranged in patterns in window frames even plate glass could achieve some artistic value. Arrangements of window frames and their placement was an important consideration for architects and engineers who had to balance style with the structural integrity of their buildings.

Manufacture

In the 18th century panes of glass were made in one of two ways. For Broad Glass a tube of glass was blown and the ends were cut off. The resulting cylinder was slit along its length. Under heat it opened into a broad plate. The technique of Crown Glass was popular in France and involved spinning a sphere of glass. Centrifugal force spun the soft, heated glass into a flat disc. The edges were cut off to create a square and panes cut from that. The center pane was left with the scar of the glassworkers tool, called a pontil mark, and became known as bull’s-eye glass and was used only where visibility was not important.

Function

Glazed windows (windows with glass in them) significantly improved visibility by allowing light to enter a room without air entering. Glazed windows were not common in everyday homes until the 16th century. These window panes were found in the ruins of Fort Ticonderoga and show how even utilitarian buildings by the 18th century used windows to illuminate barracks and storehouse spaces.

Culture

Many of the windows of the fort today have panes of bull’s-eye glass, identifiable by the thick blob of glass in the center. In the 18th century this was a by-product of the Crown Glass method of making plate glass, and was not commonly used for windows. French accounts from the period the fort was built indicate that plate glass was available in Canada and the fort’s storehouse contained 5 boxes of plate glass in 1757. The bull’s-eye glass windows are a product of the 20th century reconstruction of the fort. The designers wanted glass that was clearly handmade to make their reconstruction feel authentic.