Water is not the same everywhere. In some areas the water has a high content of minerals, such as calcium and magnesium. This water is called hard water [source: Britannica]. After the water has evaporated from a surface, such as a window, it will leave spots known as calcium deposits or lime scale. At first it's not very noticeable, but after a while the deposits build up and there's a thick whitish glaze. In the early stages, these deposits are easy to get off, but over time as they are baked on by the sun, they become more difficult to remove, giving your windows a rough texture and unpleasant haziness [source: Glass polishing]. Here is a foolproof way to get rid of hard water stains on your windows.

  1. Prepare a mixture of half water and half vinegar.
  2. Soak a towel in the solution.
  3. Press the towel onto the rough spots on the window. Let it sit there for a minute or two. The acidity in the vinegar will soften the mineral deposits making it easier to wipe off. You can also try draping the towel over the window, if it will remain hanging and not fall down.
  4. Wipe and press the towel on the window until the spots disappear. You may have to repeat the process several times until all the spots are gone.
  5. Dry the window with a rag. You may want to shine the window with a window spray.

Another tried and true way to remove hard water spots from your windows is by rubbing them with some white wine [source: BBC].