#shells

How did people make windows translucent in eras without glass or when it was prohibitively expensive by Lu Lei 鲁磊

Seashell windows (especially using "sea moon shells海月贝") were not common in ancient China. They were mostly found in coastal areas like Fujian and Guangdong, where shells were abundant. Ordinary people used paper windows, while seashell windows -due to their complex craftsmanship and scarcity -were mostly used in palaces, temples, or wealthy homes. However, seashell windows had drawbacks: poorer transparency than paper windows; fragile and hard to maintain; could not be opened or closed easily, often fixed as decorative panels rather than functional windows.

Most ancient windows were made of sturdy paper (like mulberry bark or cotton paper), treated with tung oil or rice paste to resist wind and moisture. Multiple layers of paper improved insulation, reducing cold air from entering.

Though thin, paper windows allowed light in while wooden frames provided some insulation. Traditional buildings also used smart designs to stay warm: facing south to maximize sunlight; overhanging eaves to block summer heat but let in winter sun; double-layered windows (e.g., "lift-and-hang windows") -outer paper layer for windproofing, inner wooden shutters or curtains for extra insulation at night.