What is Borosilicate Glass

glass inspectionBorosilicate glass is a type of glass made of silica, boric oxide, potassium oxide, zinc oxide and trace amounts of calcium oxide and aluminium oxide. It is known for its heat resistance and physical durability, and is useful in many applications that involve temperature changes.

The presence of boric oxide and silica allows the glass to become thermal shock resistant. This resistance prevents the borosilicate glass from warping or deforming when exposed to temperature changes. Low thermal expansion allows the glass to maintain integrity when transferred directly from a cold area to a hot area. The approximate maximum thermal shock range (the withstandable temperature difference) of borosilicate glass is 170°C (340°F).

Borosilicate glass can also withstand blunt force better than other glassware. It is also capable of withstanding corrosion when exposed to acidic environments. In fact, borosilicate glass is so resistant to chemicals, it is used to safely store nuclear waste.

glass waferWhat is Borosilicate Glass Used For

Borosilicate glass has a wide variety of applications, including:

  • Laboratory glassware
  • Pharmaceutical glass tubing
  • Cookware and kitchen implements
  • Optical equipment
  • Lighting technology
  • Premium glassware
  • Glass wafer

What Is the Difference Between Borosilicate Glass and Soda Lime Glass

Soda lime glass gets its name from its chemical composition, a mixture of silica, soda (sodium oxide) and lime (calcium oxide). It is extremely popular, and accounts for 90 percent of glass manufactured worldwide. While it is less expensive than borosilicate glass, it is also less durable. Soda lime glass is susceptible to temperature shock and can not handle extreme changes in heat. It can only maintain integrity at normal temperatures.

Soda lime glass has a coefficient of thermal expansion that is more than double that of borosilicate glass, meaning soda lime glass will expand more than twice as fast when exposed to heat. This will frequently lead to breakage. Soda lime glass is made with less silica that borosilicate glass as well, which also increases the likelihood of breakage.  

Borosilicate Glass Stats

Coefficient of thermal expansion = 3.2 x 10-6 1/K
Annealing temperature = 470 - 640°C
Vicat softening temperature = 460 - 840°C
Transition temperature = 440 - 560°C
Shear modulus of 26.5 – 27 GPa
Knoop hardness of 400 – 480 at 20°C