Historic Types of Window Glass

Roman Empire

• Crude, flat-glass -- used for windows -- was a Roman invention. Glass windows of the 1st century A.D. were blown glass, produced by spinning a bubble of molten glass. This process resulted in a thick, flat piece of opaque material with a bull’s eye center where the blow pipe was attached. These small windows let in light, but did not have the transparency needed to see out.

Dark Ages

• After the fall of the Roman Empire, glass making improved as a result of better materials and more efficient furnaces. Ash wood used to fuel the furnaces made it possible to melt the glass at lower temperatures. This resulted in a lightweight glass window.

Middle Ages

• From the 12th century on, stained glass was used to adorn Christian cathedrals in England and France; the most famous of these are the pilgrimage cathedrals of Chartres in France, and Canterbury in England. Transparent crystal-glass was invented in Murano Italy -- in the mid-15th century -- by Angelo Barovier.

Age of Revolution

• By the dawn of the 18th century, the French discovered grinding and polishing techniques that enabled the production of plate glass. These windows were very expensive. Political and industrial revolutions that followed led to the development of a process to create flatter and less expensive panes of glass. Flat-glass windows were used in all types of building construction by 1860.

The Modern Age

• Machines were invented to mass-produce sheets of window glass during the early 20th century. The development of automobiles led to new window features, such as laminated windshields and tempered glass. The production of float-glass in 1959 replaced flat-glass in residential and commercial construction; it remains the primary method of glass production in the 21st century.