Crown glass (window)

This was then transferred from the blowpipe to a punty and then flattened by reheating and spinning out the bowl-shaped piece of glass (bullion) into a flat disk by centrifugal force, up to 5 or 6 feet (1.5 to 1.8 metres) in diameter.

To fill large window spaces with the best glass, many small diamond shapes were cut from the edge of the disk, and then some might be halved into triangles.

Crown glass window panes with ceramic frames have been found at Soba East, the medieval capital of Alodia.

[2] The process of making crown glass window panes was perfected by French glassmakers in the 1320s, notably around Rouen, and was a trade secret.

The early 20th century marks the move away from hand-blown to machine-manufactured glass such as rolled plate, machine drawn cylinder sheet, flat drawn sheet, single and twin ground polished plate and float glass.