Welcome to the Glass Age

33 and cylinder glass. Both began by blowing, a process that, without intervention, tends to create spheres. In crown glass a hole is created in the ‘bubble’ which is then spun rapidly so that it opens out into a disc with characteristic circular markings. In cylinder glass a large sphere is allowed to extend vertically under the influence of gravity to create the required shape. Once made, the cylinder can be opened into a sheet by making an extended crack along one side and opening the cylinder up inside a hot furnace using long wooden rakes. Such methods were incapable of creating distortion free Figure 2.5. Stained glass window from a church. Source: Pixabay.