The jars that contain your favourite jam are made from soda-lime glass, but the glass pipes used for smoking are made from borosilicate glass.
The reason is simple - regular glass (soda-lime glass) has a very high coefficient of thermal expansion, so it likes to explode with extreme temperature changes.
On the other hand, Borosilicate glass has a very low coefficient of thermal expansion, so it sits pretty whether water is boiling or freezing.
Thermal expansion isn’t the only reason borosilicate glass is better than soda-lime glass; it’s also stronger, more durable and more inert to chemicals, which is why it’s used for beakers, bottles and measuring cups in laboratories.
What is borosilicate glass?
Borosilicate glass is made from high concentrations of boron trioxide and silica, fusing to form glass. The glass is different in composition to regular glass, designed to create mechanical and chemical durability.
Because borosilicate glass is harder and stronger than regular glass, it can be moulded into more complex shapes like glass pipes and bongs.
Otto Schott invented borosilicate glass in the 1880s. The chemical composition of modern borosilicate glass is the same, except today’s chemicals, are more refined, and the manufacturing process is more consistent.
Why is borosilicate glass better?
Borosilicate glass is harder, stronger and more thermally resistant than soda-lime glass, making it ideal for intensive applications.
For glass smoking pipes and bongs, borosilicate glass is crucial for safety and weight. Soda-lime glass isn’t suitable for the temperatures glass pipes create unless it is very thick, which increases cost and weight, making the glass pipe difficult to use.
Borosilicate glass is superior to soda-lime glass in every aspect, although it is more expensive, so it is reserved for specialist applications. For example, you’ve probably heard of Pyrex glass cooking ware, which is borosilicate glass.
Borosilicate glass is compatible with faster temperature changes than soda-lime glass, so it’s suited to applications with heat.
Is borosilicate glass unbreakable?
No! Borosilicate glass will break if you drop it, and especially in the cases of glass pipes and bongs, which have very thin borosilicate globes.
However, borosilicate glass won’t break with temperature fluctuations unless you do something extreme like fill a frozen beaker with boiling water. Doing this would probably push the physical properties of the glass too far.
How can you tell if the glass is borosilicate?
Borosilicate glass almost disappears underwater because of its similar refractive index, while soda-lime glass is clearly visible.
Another way to spot borosilicate glass is by looking at the edges; soda-lime glass has a blue-green hue, while borosilicate glass is colourless.
Can you recycle borosilicate glass?
You can only recycle borosilicate glass at special facilities. Borosilicate glass contains chemicals that alter the melting properties of regular glass, rendering it unusable. Broken borosilicate glass enters the trash stream unless sent to a dedicated recycling facility, which is rare in the UK. Contact your local council for guidance.