Borosilicate glass vs Soda-lime glass
Borosilicate glass and Soda-lime glass are commonly confused, and 1 measured property separates them — density most clearly.
Borosilicate glass vs Soda-lime glass
Borosilicate glass
Glass with boron in it, which barely changes size when heated — the reason an oven dish does not shatter and a drinking glass does.
Soda-lime glass
The commonest glass — silica with soda to lower its melting point and lime to stop it dissolving in water.
| Property | Borosilicate glass | Soda-lime glass |
|---|---|---|
| Crystal system Only one of the two has a figure we can stand behind, so there is nothing to compare. | Not known | amorphous |
| Density | 2.2–2.25 g/cm³ | 2.44–2.55 g/cm³ higher |
| Refractive index Only one of the two has a figure we can stand behind, so there is nothing to compare. | 1.47 | Not known |
| Thermal conductivity Only one of the two has a figure we can stand behind, so there is nothing to compare. | 1.1–1.2 W/(m·K) | Not known |
Choosing between them
Borosilicate glass is recorded as a substitute for Soda-lime glass — better at temperature.
What it gives up: Several times the price, harder to melt and work, and it cannot be float-formed easily — which is why windows and bottles are not made of it.
In this application, on the evidence cited above.
Why these get confused
sold under one trade name in some markets: American kitchen 'Pyrex' was reformulated to tempered soda-lime, which is strong against impact and no better against heat
The confusion is a real and documented one, not a resemblance we have invented.