Satisfying the Curious Customer: Why is Glass Transparent?

Our industry is full of glass experts. And I have heard those experts respond to a tremendous range of questions regarding glass and glazing. What is the thermal performance of this window? Will this insulating glass unit experience condensation in the winter? Can this product withstand hurricane-force winds? And these experts are working to answer even more complicated questions, like what is the cradle-to-grave life cycle of this glass unit?

While glass experts field these more practical product questions on a regular basis, I wonder how often they receive perhaps the most rudimentary query about glass: Why is glass transparent? Why does molten sand turn into a transparent, solid material after cooling? And, that leads to other curious questions. If visible light and heat can pass through glass, are ultra-violet rays allowed through as well? Can you get a sunburn through glass?

A recent TED-Ed talk by Mark Miodownik answers these questions in an animated video. Perhaps it will prove a useful educational tool for any curious customers out there.

Devlin is editor of Glass Magazine. Write her at


I have wondered a few times if I could get a tan through a car window on a long road trip. Now I know why I can not.