“The invention of glassmaking was . . . dependent upon ceramics and in fact, in scientific circles, glass is considered a ceramic. The first glasses . . . were glazes. The Egyptians discovered that by mixing ashes (potassium), ground-up sand (silica), and natron (salt from dried lake beds), they could give their pots a shiny coating. What they were doing was “fluxing” the silica. They learned by accident or through experiment that if they took a bowl of this glaze, especially one that had more flux and less silica, from the kiln while still molten, it could be poured into a clay mold and then cooled to form an object. Glass was equated with gems and was as highly prized.”

—Suzanne Stauback, from Clay: The History and Evolution of Humankind’s Relationship with Earth’s Most Primal Element, 2005.