Before float glass (also called flat glass), each piece of glass was individually poured and polished. This was a time consuming and expensive process that left the contours of glass uneven. Pilkington invented a method of floating the glass in a bath or iron tin, leaving both sides of glass perfectly smooth.
Float glass took seven years to perfect. They applied for the first patent Dec. 10, 1953.
In 1962, Pilkington’s company decided to license the invention albeit with strict non-disclosures. Licensees could never reveal production processes and must continue paying royalties even after patents expired.
Pilkington protected their IP so well that the US Dept. of Justice successfully sued in 1994 for violations of anti-trust provisions. They argued that Pilkington was, in effect, conspiring to artificially inflate the price of glass.