Hardwater Stain Removal

Clear Choice Window Cleaning employes the current industry standard  for hard-water stain removal. We use of an oxide polishing agent,  abrasive pads rated for glass and rotating electric buffer. The glass is  first cleaned, then polished, than cleaned again, then a hydrophobic  product is applyed to form a transparent, micro thin barrier to protect  the glass against future water damage.

Glass Corrosion is an extensive topic. To aid you in your research on  the subject we have included excerpts from this excellent article  published in Window Cleaning Magazine issue #14.
Title: Understanding Glass Corrosion
By: Henry Grover Jr.

“Simply put, glass can and does corrode. It can be brought to  complete dissolution by both acids and alkalis. Even rain water will  corrode or etch glass. Water acts like an acid in that it is much more  prone to selectively go after the alkaline compounds in glass. It does  take many years. but its effects can be felt with your fingertip. The  outside surface of an old storm window will always be noticeably more  rough than the inside surface. Apart from corrosion by weathering, all  glass surfaces are hydrophilic (water loving). So there is a molecular  vapor on the surface at all times. Therefore, even the most smooth  surfaces will have potholes and peaks about five microns across. These  micropores can becomes filled with organic and mineral contaminants,  which is literally bond to the glass.

Mineral deposits can and do cause corrosion. Water drops continue to  reform and dry on top of the same deposits. Over time, this increases  the pH of the drop as water evaporates. Once the pH goes beyond 9, total  dissolution occurs. Both the reaction byproducts and the minerals in  the water are left behind. They become concentrated around the outer  edge of what I call the spot ring. When they are removed with an optical  grade polishing slurry, the same shape of that ring can be seen as a  clear distortion in the surface. This is especially noticeable on dark glass.

In view of this information, it makes sense to especially protect  those glass surfaces that are exposed to concrete or brickwork runoff or  ground water from sprinklers. This can be done with a quality  hydrophobic sealant. A very regular maintenance program should also be followed, which might require intermittent removal of newly formed spots  and replenishing of the hydrophobic coating, depending on the severity  of the conditions.”