Eli5: Why does water that dries on glass leave “streaks” or grey markings on the glass?

Question

Eli5: Why does water that dries on glass leave “streaks” or grey markings on the glass?

In: 192

Answer 1

Tap water has lots of little bits of rocks, metals, salts, bacteria and other funky stuff inside it. When all the water dries up, the stuff is left behind leaving a streak on the glass.

Answer 2

Tap water has lots of little bits of rocks, metals, salts, bacteria and other funky stuff inside it. When all the water dries up, the stuff is left behind leaving a streak on the glass.

Answer 3

Tap water has lots of little bits of rocks, metals, salts, bacteria and other funky stuff inside it. When all the water dries up, the stuff is left behind leaving a streak on the glass.