petrochemical and therefore not a substance I like to use regularly, but it definitely has its household uses. And when it comes to cleaning windows and mirrors, there is nothing I've tried that is as effective as rubbing alcohol. A little goes a long way, and a 16-ounce bottle typically costs around $1. It also cuts through crusties and dries without streaking better than anything else I've tried, including products that are made specifically for windows and mirrors.
As I researched this topic, I was surprised to learn just how many other handy household uses isopropyl alcohol has!