The mighty Borosilicate Glass!

While doing certain household experiments as a school boy, I was shocked in two incidents to see my experimenting work spoiled. First one occurred when the glass bottle in which I had poured hot water broke down and the other one when I poured water in a hot glass bottle ('Horlicks bottle', as it was called then) - it cracked and fell down in pieces! My efforts to set up a 'home laboratory' was thus shattered!
Then how these school laboratory test tubes are intact even when heated much, I wondered. The fact is that they are made of a different glass material called Borosilicate glass that is made from Silica and Boron oxide. This glass is resistant to thermal expansion. Called as 'Pyrex', this glass bears a mark with the word Corning or Duran in it. It is durable, chemical and heat resistant . That is why it is used in equipments of Chemical laboratories and in making injection ampoules.

This wonder glass is also present in kitchenware like Milk boiling jars, and cooking vessels made of it are also micro-oven compatible!