Short answers, pulled from the story.
Glass is an amorphous, non-crystalline solid, and silicon dioxide is its common fundamental constituent. Soda-lime glass, which accounts for over 75% of manufactured glass, contains about 70 to 74% silica by weight along with lime, magnesia, and alumina.
Archaeological evidence suggests human glassmaking dates back to at least 3600 BC in Mesopotamia, Egypt, or Syria. The earliest known glass objects were beads from the mid-third millennium BC, and true transparent glass did not appear until the 15th century BC.
No, once glass solidifies it stops flowing, so old windows that are thicker at the bottom simply reflect imperfect past manufacturing. A 2017 study of medieval glass from Westminster Abbey dated to 1268 calculated a maximum flow rate of 1 nanometer per billion years.
Flat glass is made by the float glass process, developed by Pilkington Bros. in England in the 1950s, in which molten glass floats on a bath of molten tin to form distortion-free sheets. The process was developed between 1953 and 1957 by Sir Alastair Pilkington and Kenneth Bickerstaff.
Color in glass comes from electrically charged metal ions distributed through the material, each absorbing specific wavelengths of light. Cobalt oxide produces deep blue, chromium yields dark green, cadmium sulfide produces imperial red, and copper(II) oxide gives turquoise.
Major types include soda-lime glass for windows and tableware, borosilicate glasses such as Pyrex and Duran for labware and cookware, lead glass for brilliant glassware, and fused quartz for high-temperature uses. Beyond silicates, glasses can also be formed from metals, phosphates, borates, chalcogenides, and fluorides.