A New Glass for a New Era: Borosilicate Glass 

Glass has shaped human culture for 3,500 years. Common sodalime glass is made from soda ash (sodium carbonate) and lime (calcium carbonate).

With the rise of modern chemistry, glassmakers developed new glass formulas to create glasses with new, desirable properties.

Through careful experimentation, German glassmaker Otto Schott (1851-1935) discovered that adding boron to glass recipes produced a borosilicate glass resistant to thermal expansion.

Only in the past few years have scientists learned why adding boron makes glass expand and contract less than sodalime under changing temperatures.

In sodalime glass, sodium atoms soften the glass, making it easier to shape. But sodium also makes glass expand when it heats up. When sodium atoms are hot, they vibrate and expand more than most other atoms in glass.

In borosilicate glass, softening is done by the added boron atoms, so less sodium is needed. As a result, borosilicate glass expands only one-third as much as sodalime glass.

In Corning, NY, scientists Eugene Sullivan (1872-1962) and William Taylor (1886-1958) developed a new borosilicate formula. This borosilicate glass, called Nonex for “non-expansion” glass, performed well as railroad lenses.

Using a sawed off borosilicate glass battery jar like this one, Bessie baked a perfect sponge cake for Jessie to share with his co-workers.

Bessie Littleton’s kitchen experiment led to another variation in the recipe for borosilicate glass. The new glass became known as Pyrex, and was shaped into glass baking dishes.

An effective marketing campaign made Pyrex a household brand. By 1919, over 4 million Pyrex dishes in about 100 shapes and sizes filled American kitchens.

The thermometer also became part of the modern household first aid kit. Monitoring the family’s personal health safely and accurately became possible with a borosilicate glass thermometer that wouldn’t easily break.

Continued efforts at innovation led to changes of the Pyrex measuring cup, including its handle.

Further testing and user feedback produced a radical new design: a handle attached only at the top, allowing the measuring cups to stack.

Borosilicate laboratory glassware like Pyrex (and Duran in Europe) withstands thermal shock, and it is more chemically resistant than sodalime glass, making it ideal for a wide variety of chemical uses.

This 20-ton, 200-inch (5-meter) disk is one of the world's largest pieces of cast glass. It was to serve as the gigantic mirror for the Hale telescope on Mount Palomar near San Diego.

In 1934, the first attempt to make the mirror failed when the casting mold broke, but the second attempt succeeded, inspiring future engineers and artists.

Two crews spent 6 hours pouring over 100 ladles of hot borosilicate glass into the improved mold. After 10 months of cooling in an annealing oven, the disk was ready.

The disk traveled to California on a whistlestop tour. After arriving at Mt. Palomar, the surface was ground into shape, polished, and coated with aluminum.

The finished mirror became a key part of the most powerful telescope yet, seeing first light in 1949.

Until the invention of borosilicate glasses, flameworkers were restricted to using sodalime glasses.

This scene depicting Marie Antoinette is constructed from several small-scale flameworked sculptures of sodalime glass that have been attached with animal glue. Melting the elements together or making them much larger would have risked breakage due to thermal shock.

Craftsmanship in flameworking reached a high point with the biological models of Leopold (1822-1895) and Rudolf (1857-1939) Blaschka. Their brilliant works constructed of finely detailed flameworked sodalime glass elements, were attached with adhesives to avoid the risks of thermal shock.

Jill Reynolds (1955-) uses borosilicate glass because it is more amenable than most other glasses to being interconnected. Letters, made of small glass rods and larger tubes filled with a blood-like red liquid, stand in for the models of proteins created during DNA replication.

Luke Jerram (1974-) explores the tension between the beauty of his glass sculptures, the deadly viruses that they represent, and the global impact caused by these diseases. Borosilicate glass is the ideal choice for such sculptures because its resistance to thermal shock more readily allows for such complex constructions.

Ginny Ruffner (1952-) adapted her knowledge of harder, borosilicate glasses, commonly used in scientific glassmaking, to art. Its tolerance for extreme temperature variance enabled Ruffner to create larger compositional sculptures with many separate elements interconnected.

To give the impression of sound waves flowing through the glass, Geoffrey Mann (1980-) has taken advantage of the unique ability of borosilicate glass to be heated and manipulated in one local area while the rest of the object can be left rigid at much cooler temperatures. Initially formed into clean, symmetrical vessels, the objects in this series were distorted by selectively heating and softening certain areas to achieve the impression of movement.