float glass (since 1952)
More or less pronounced drawing lines are characteristic for drawn glass. Only the development of float glassmade glass that was both perfectly even and cheap a reality.
The idea of pouring glass onto a bath of molten metal had been advanced by Henry Bessemer in 1900. But the technical difficulties with this method were such that it was only at the end of 1950 that Alastair Pilkington succeeded in producing float glass.