One of the most suitable and common types of glass used in optics and often used in conjunction with flint glass (they are of different refractive indices) to make up achromatic lenses. Lighter plastic equivalents of crown glass used for spectacle lenses are Perspex acrylic and CR39.
a method of producing glass in which a globe is transferred from the blowpipe to a pontil or punty, reheated and then spun until it opened up into a large flat plate - a table of crown glass. It often has a greenish tinge, curves slightly and can have small radial imperfections, all of which can give the glass a wonderful reflective quality. While more costly to produce through the wastage associated with its circular shape, because it does not come into contact with any surface during manufacture, it is more transparent than cylinder glass.
Sheet glass made by blowing a parison, cutting it open, and rotating it rapidly, with repeated reheating, until the centrifugal force has caused it to become a flat disk. After annealing, the disk is cut into panes of the required shape and size. " Bull's eye" panes come from the centers of the disks and preserve the thickened area where the parison attached to the pontil.
Crown glass was an early type of window glass. In this process, glass was blown into a "crown" or hollow globe. This was 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.