How glass sheets used to be made - GIF

[jajoma]

This is a way to make glass window panes that pre-dates the float glass which came into use around the 1920/30s. This technique makes glass panes called "cylinder glass". Another technique is called "crown glass", which is older. For this technique the glass blower spins the molten glass ball to create a disk, which could get up to 5' in diameter. Squares/rectangles/diamonds of glass would be cut out of the disk leaving the centre, often is reused as a "Bulls-eye"in windows. As the disks taper from thick at the centre to thin towards the outside of the disk, the sheets of glass are not uniformly thick with one edge thinner than the other. Some people pulling apart old windows and seeing the different thicknesses, theorized that the glass had flowed over time, a myth. Casting and rolling glass was also used for plate glass, mirrors, glass floors/slabs. By the way where is the video sourced from?