The insulating glazing unit, consisting of two glass panes bound together into a single unit with a seal between the edges of the panes, was patented in the United States by Thomas Stetson in 1865. It was developed into a commercial product in the 1930s, when several patents were filed, and a product was announced by the Libbey-Owens-Ford Glass Company in 1944. See note 25. Their product was sold under the Thermopane brand name, which had been registered as a trademark in 1941. The Thermopane technology differs significantly from contemporary IGUs. The two panes of glass were welded together by a glass seal, and the two panes were separated by less than the typical of modern units. The brand name Thermopane has entered the vocabulary of the glazing industry as the genericized trademark for any IGU.
