There was no question of the mechanical process driving the hand-blown process off the market immediately. The quality of the former was poor, but considerable increase in output made it attractive. The cylinder drawn process, however, was to become less and less competitive with the American Colburn and Belgian Fourcault patented processes for producing sheet glass by drawing a continuous ribbon of flat glass. Although Pilkington had considered the Fourcault process as early as 1903 and had obtained an option on it for this country, it had been rejected in favor of the cylinder drawn method.
In the early 1920s Pilkington co-operated with the Ford Motor Company of America in developing the continuous flow process, while at the same time itself working on a method of continuous grinding and polishing. Continued development on the Fourcault process gradually eliminated many of the technical objections, which had led Pilkington to its earlier decision, so that it slowly overtook cylinder-drawn in terms of cost as well as output. At the end of the 1920s, when Pilkington was considering abandoning sheet glass, the successful development of a third continuous flat drawn process completely changed the position. This was the PPG process, which Pilkington adopted in 1931.