The on-line resource for all your replacement and authentic restoration window glass needs! Here is a brief history of the glass making milestones in America.
Modern window glass (commonly known as Float glass) is produced by floating the molten glass on top of a ribbon of molten metal to give a uniform thickness and a distortion-free surface. Prior to this invention, window glass was produced using a variety of different methods. From the 1700’s to 1850, some of the first window glass was mouth blown and whirled into a large disk. This glass was cut into panes and graded based on clarity and overall quality; the highest quality glass would then be used in sections of the building that were most visible. This process was known as Crown Glass and it resulted in glass that was heavily distorted and very small in size.
From the mid 1800’s until the early 1900’s, the preferred method was Mouth Blown Cylinder Glass. The glass was mouth blown into cylinders and then flattened into sheets by hand. This process produced glass containing various imperfections both within the glass and on its surface, but was of better quality then previous methods and produced larger panes of glass.
The turn of the century heralded great innovations in glass making. The first was the invention of the “Lubbers” machine by John Lubbers. This machine could produce Mechanically Blown Cylinder Glass in larger cylinders of glass up to 40 feet. The glass would then be placed in a flattening furnace, similar to mouth blown cylinder glass, and cut into panes. This process would eventually replace the traditional mouth blown method. Factories during this time were also producing Polished Plate Glass. This was done by casting molten glass into a tray and polishing both sides of the glass until most flaws were removed. The finished product was of good quality with the advantage of producing large sheet sizes of varying thicknesses.
Beginning around the First World War, the Fourcault Process was invented. This machine was able to draw glass from its molten state into sheets. This was an improvement over the machine cylinder process as it removed the surface imperfections created by the flattening of the sheets and also took out the unwanted green tint. Still the glass had a slight distortion on the surface ( mostly drawn vertical lines), but this process would eventually replace the “Lubbers” machine cylinder process.