Mirror glass is thick, flat, high-quality flat glass that was formerly ground and polished into a distortion-free, crystal-clear surface. The name refers to its use for mirrors, but mirror glass was also used as premium window glass for large, clear panes.
Application
Historically, mirror glass was made as cast plate glass: molten glass was poured onto a casting table and rolled into a sheet. Because this surface was rough and dull, the plate had to be ground and polished on both sides. This allowed large, thick and perfectly flat panes, far larger and clearer than the blown window glass of the time. Such glass was costly and was used for fine mirrors, shop windows and prestigious windows.
A mirror itself is created by applying a reflective layer to flat glass. This was once done with tin amalgam; later a thin silver layer (silvering), sometimes aluminium, was applied to the back and finished with protective coatings.
Characteristics
Modern “mirror glass” is almost always float glass. Because float glass emerges perfectly flat and distortion-free from the float process, grinding and polishing have become unnecessary. A modern mirror is therefore float glass with a reflective silver or aluminium layer on the back. In trade, mirror glass still often means clear, high-quality flat glass.
Related terms
- glass
- building glass
- double glazing
- wired glass
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