Water marks on glass are mineral deposits resulting from water (or moisture in humid climates) that has dried on the glass, or from water that is trapped between two pieces of glass and dried. Most water marks are dried calcium. No amount of glass cleaner will remove them as they actually adhere to the surface of the glass. Removal of water marks can be done by using one of two methods.
The first method is to purchase some pumice powder. Dry pumice powder is simply rubbed over the surface of the glass using your fingers or thumb tip. This rubbing motion with pumice removes smaller water marks. The pumice is only sold in specialty glass stores and can’t be found in a hardware store.
The second method (for larger surfaces) is to use a special 3M glass cleaning pad in a rubbing motion to remove the water marks. These pads will not scratch the glass and can be used dry or with a water/soap mix. Soaking the glass for 10 minutes in a soap or detergent warm water mix helps soften the hardened mineral deposits and the pads will then easily remove them. (Do not use other pad types as they may scratch the glass). 3M does not specifically sell a glass cleaning pad (we use a special 3M pad that is designed for a different use but works great on glass, hence we call it our “glass cleaning pad”). One place users can find the special 3M pads is on our website.
—CrystalEdge