The quality of building glass has improved dramatically over the centuries: from thick, wavy and tinted handmade glass to mirror-flat, clear float glass in large formats with high insulation value. This development followed four lines: clarity, flatness, size and performance.
Application
In early glass history, window glass was thick, uneven and small. Hand techniques such as crown glass and later cylinder or drawn glass produced panes that often had a greenish tint, air bubbles and waviness. The view through them was distorted, and the available sizes were limited.
With drawn window glass (Fourcault, early 20th century), production became mechanised. The glass grew more even and available in larger sheets, though slight distortion remained. An intermediate step toward mirror-flat glass was grinding and polishing cast glass (plate glass), which was clear but labour-intensive.
Characteristics
The major breakthrough came with the float process (1959, Pilkington), in which molten glass floats over a bath of molten tin. This naturally creates a mirror-flat, distortion-free surface of constant thickness. Float glass is clear, available in large formats, and today forms the basis of almost all building glass.
Alongside clarity and flatness, performance also improved. Single glazing gave way to double glazing and later to high-performance and triple glazing, fitted with coatings and inert-gas fills. Modern building glass thus combines optical quality with greatly improved insulation.
Related terms
- glass
- building glass
- double glazing
- mirror glass
- glass corrosion
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