Final answer:
The most common type of glass used in buildings during the 21st century is float glass, thanks to its clarity and uniformity, which makes it suitable for large windows in modern architecture.
Therefore, the correct answer is: option 2: Float
Step-by-step explanation:
The float glass was developed in the late 1950s, this technique involves pouring molten glass onto a bed of molten tin, where it spreads out to form a flat surface.
As the glass cools, it solidifies into a smooth and uniform sheet which is ideal for use in windows due to its clarity and uniform thickness.
Early architectural innovations, like the Crystal Palace, paved the way for the modern use of glass in buildings by showing that large amounts of glass could be supported structurally.
The primary component in glass is silica, and it remains transparent even with the addition of color. This has allowed for the creation of beautiful stained-glass windows, particularly in sacred buildings.
Modern architecture has further embraced glass thanks to its availability in large, consistent sheets made possible by the float glass process. This has led to building designs where walls can virtually disappear, being replaced by large expanses of transparent or colored glass to create a sense of openness and bring natural light indoors.