Crown glass was an early type of window glass. In this process, glass was blown into a "crown" or hollow globe.
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. The glass was then cut to the size required.
Crown glass is one of many types of hand-blown glass. Other methods include: broad sheet, blown plate, polished plate and cylinder blown sheet.