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Float Glass
The workhorse flat glass made by floating molten glass on a bath of molten tin. Used as the substrate for almost every other architectural glass type — including the outer plies of a vacuum-insulating glass unit.
Why it matters
Almost every other glass type starts as a float glass substrate:
- Tempered glass is float glass that has been heat-strengthened.
- Low-E glass is float glass with a sputtered metal-oxide coating.
- Laminated glass is two or more plies of float glass bonded with a PVB or SGP interlayer.
- Vacuum glass uses two float glass plies as the outer walls of the VIG unit.
Typical thicknesses
Float glass for architectural use ships in 2 mm to 19 mm thicknesses, with 3 mm, 4 mm, 5 mm, 6 mm, 8 mm, 10 mm, and 12 mm being the most common stock sizes. VIG units typically use 3 to 4 mm plies for the outer walls.
Limitations
Float glass breaks into large, dangerous shards unless it is further processed (tempering, laminating, or both). Architectural codes almost always require one of those safety treatments for vision glass in human-occupied spaces.