You've just finished your shower. The bathroom is warm and comfortable, but when you go to shave, put on your makeup, or fix your hair, you encounter the same problem as so many others. The mirror is fogged up again.
For most people, it's an everyday problem that can be quickly solved by wiping the glass with your hand or a towel. But few people think about why the mirror fogs up in the first place.
In fact, condensation on the mirror is a clear sign that the bathroom contains more moisture than the cold surfaces can handle.