Why did such an important discovery occur so late in the … history of glass, and why was an accident necessary to bring it about?
– Donald Stookey, 1977
Crystals are usually a glassmaker’s enemy. When they form in glass, crystals can change the properties of the material in unwanted ways. Corning chemist Donald Stookey saw crystals differently.
One night in 1954, he put a piece of experimental glass into a furnace. The next morning, he discovered that the furnace had overheated. He was sure he would find a pool of melted glass inside. Instead, he found an opaque solid that was so strong it bounced when he accidentally dropped it. Microscopic crystals had formed, changing the glass into a new material that Stookey called a glass-ceramic.
Stookey knew he could use heat and chemistry to control crystallization. Maybe it would be possible to form different crystals in different glasses. That would mean glass-ceramics could be tailored to have a remarkable range of properties. Stookey was right. Today, glass-ceramics are used to make everything from heat-defying cookware to exotic optical devices.
A Recipe for Glass-Ceramic
- Make the glass, adding a special material—a nucleating agent—to the raw ingredients of the glass batch. The nucleating agent forms microscopic particles called nuclei
- Heat the glass again. Crystals will grow on the nuclei.
- The result is a new material, a glass-ceramic, with properties different from the original glass.
The secret to making a glass-ceramic is control. Scientists select the exact temperatures and ingredients needed to make crystals grow in the glass. When enough crystals have formed, the glass becomes a new material: glass-ceramic.