All the components of glass can be found in two places: the beach and the laundry room. It’s possible to melt pure white-silica beach sand into glass, but only at temperatures of 3,000 to 3,500°F. Washing soda, lime or borax (a traditional laundry aid) added to the sand disrupts the quartz-crystal structure of silica and reduces the required temperature to a more practical, though still dangerous, 2,000°F, which I achieved with a backyard grill and a vacuum cleaner. Glass is thought to have been discovered around 7,000 years ago by Phoenician merchants when cooking fires were built over sand that, by chance, had some of these substances mixed in.
Soda-lime glass has the lowest melting point but must be cooled slowly to avoid shattering from thermal stress. Borosilicate glass, commonly known as Pyrex, melts at a higher temperature but can be cooled more rapidly. I made a medallion out of each and just left them in the fire as it died down over a few hours.
Although making glass from sand is satisfyingly primal, starting with actual glass is more practical. Old test tubes yield high-grade borosilicate glass; wine bottles, colored glass. Watch out—it’s all very sharp and hot when molten!
Five amazing, clean technologies that will set us free, in this month's energy-focused issue. Also: how to build a better bomb detector, the robotic toys that are raising your children, a human catapult, the world's smallest arcade, and much more.