Borosilicate Glass - Properties of Borosilicate Glass (Pyrex/Duran) by Goodfellow Ceramic & Glass Division

1. Dan Askew says:

   August 22, 2016 at 3:49 PM

   Can you place the beaker directly on an electric heating coil (electric stove) to bring water to a boil on a high heat setting? Is there any danger of the beaker breaking under such conditions?

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   • William Bremer says:

     November 16, 2020 at 8:52 AM

     I would not recommend it.  Heat is not what makes glass break, per se.  What causes heat breaks in glass is the thermal differential.  Because it does not conduct heat well, it is very difficult to heat the entire article evenly.  When heating at one spot only, such as setting it on a stove burner or with a blowtorch, it tends to shatter violently.  Borosilicate glass used in lab equipment is more resistant to this. This type of glass is also  known by the trademark Pyrex by Dow Chemical.  Casserole dishes are commonly made of Pyrex.  Heating in an oven heats the entire article evenly so it does not break. Borosilicate is more resistant to thermal differential breaks than ordinary glass, and "Quartz glass" the common name for a heavy-duty industrial grade borosilicate is even more resistant. I would recommend using a metal container like cookware to boil water since  (a) it certainly won't break, and (b) being many times the thermal conductivity of glass, will boil your water much more quickly.  Supposing we ignore the potential for breakage, water in a glass beaker or flask on a heat coil would take much longer to boil because of the low thermal conductivity of glass.  Rough thermal conductivity of common materials in W/m K:
     ordinary glass: 0.8  borosilicate: 1.1  "quartz" glass: 1.4  steel: 50
     aluminum: 200 copper: 385  silver: 400 diamond: 1000
     This accounts for the prevalence of copper or copper-bottomed cookware, which is what I suggest you boil in.

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     • Canys Okanga Cyrus Legrand says:

       May 18, 2022 at 3:32 AM

       The answer was clear and perfect. Because of the low thermal expansion of the Pyrex, it will be hard to be broken by the thermal shock or thermal cracking. But I would like to understand why doing this rather than using a metallic one which is more efficient?  :-)

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