The cylinder process had two main versions in which the cylinder was created.
In the earlier version of this process, a blowing technique was used. First, a ball of glass was blown at the end of a blower’s pipe. Once the desired circumference was reached the blower would begin to create the cylinder. This was done by reheating the ball in a furnace and swinging the glass ball in a trench in a pendulum motion to stretch the ball into a cylinder shape. This took great craftsman skill and was an energy consuming process for the worker.
The later version (pictured) was mechanised and could create cylinders 13 metres high. This was done by dipping a round metal bait into a bath of molten glass which was then raised to create a long cylinder of clear glass. The advantage of this version of the process was that bigger panes could be made, and less human energy went into it.
In both versions, after the cylinder had been made, the cylinder was scored and split down one side and laid flat on the opposite side. The cylinder was then moved into a furnace where it would be softened again and would be flattened with the split edges peeling outwards. This would create a flat, straight edged piece of glass.
The advantages to this process was that in the latter version a lot less effort had to go into making the glass meaning less man-power was needed. Also, with the edges of the product being straight, panes of glass could be cut out of it, creating minimal wastage.
The disadvantage was that the surfaces could get damaged when the cylinder was split and flattened.
Information sourced from The Glassmakers by T. C. Barker and Float: Pilkingtons' Glass Revolution by D. J. Bricknell and in-house.