A pinch of boron lets lab glass survive shocks that shatter ordinary glass
Pour boiling water into an ordinary glass dish and set it on ice, and it may crack. Borosilicate glass shrugs off temperature swings about four times larger, because adding boron makes it expand only a third as much when heated. That trick puts it in labs, kitchens, syringes and even data storage.
The German glassmaker Otto Schott developed it in Jena in the late 19th century, and it was first called Jena glass. After Corning launched Pyrex in 1915, that brand name became shorthand for borosilicate in English, although since the 1940s much Pyrex-branded kitchenware has been ordinary soda-lime glass. Typical laboratory borosilicate is about 80 percent silica and 13 percent boric oxide, with small amounts of sodium or potassium oxide and alumina. It melts hotter than normal glass, which required new production methods, but it is still economical to make.
The key number is thermal expansion. Lab-grade borosilicate expands by roughly 3.3 millionths of its size per degree, about one third the rate of soda-lime glass and the lowest of any commercial glass used at scale. Less expansion means less internal stress when one part heats faster than another, so it can tolerate a sudden difference of about 170 degrees Celsius, against roughly 40 for soda-lime. It is not invincible, and rapid or uneven heating can still break it. Fused quartz performs better still but is far harder and costlier to work, which makes borosilicate the affordable compromise. It is also lighter than regular glass, because boron atoms are light.
Its chemical toughness matters as much as its heat tolerance. Almost all modern lab glassware uses it, and vials, prefilled syringes and ampoules for injectable drugs are made from it because very little sodium leaches out into the contents. Its uses extend inside the body too, sealing devices such as neurostimulators for epilepsy and cochlear implants, and it goes into artificial hips and white dental fillings. By varying the boron content, makers can match the expansion of metals like tungsten and molybdenum for airtight glass-to-metal seals.
Newer uses keep appearing. Microsoft's Project Silica in 2026 used borosilicate wafers as archival storage, with estimates that a wafer 120 millimetres square and 2 thick could hold 2.02 terabytes for more than 10,000 years.
Source: Borosilicate glass
