by Fenella Saunders
Around the first century A.D., the Romans used casts to make the first translucent windowpanes. By the fourth century, they learned to slit open glass cylinders and heat them until they lay flat, a method still used to make windows for the White House. In medieval times, the Normans created blown-glass panes by spinning hot glass into a large flat disk. Windows grew gradually cheaper due to mechanization and better glass formulas. In 1902, American inventor John Lubbers developed an automatic system for drawing a 50-foot cylinder of hot glass using a jet of compressed air. About the same time, Emile Fourcault in Belgium and Irving Colburn in the United States separately created plate glass by drawing hot gobs of it through rollers. This method banished the rippled surface seen in old windows. In 1959 Alastair Pilkington in England floated molten glass atop a smooth pool of melted tin, eliminating the need for grinding and polishing. French scientist Edouard Benedictus invented a safety glass, consisting of two panes held together by a flexible film of cellulose nitrate, in 1910. This year the Pilkington Company in England created glass coated to repel dirt the first self-cleaning windows.