There are many ways to ruin your windows. Every year I am called to try to remedy window cleaning problems due to a lack of knowledge by the homeowner.
One common problem I run into are homes in which the homeowner took it upon himself to clean his windows by hosing them down. He has seen window cleaning companies who pressure wash windows, so he figures he can save some money by doing the same.
What he does not know is that window cleaning companies who pressure wash windows use specially treated water that has no hard solids in it. The water is usually treated by running it through de-ionization tanks or by reverse osmosis. Tap water in the Treasure Valley is laden with iron and calcium carbonate and other solids that will dry on your windows, leaving a milky appearance.
Other homeowners are simply plagued by sprinklers leaving hard water residue when the wind blows sprinkler water onto the glass.
However the stain gets there, it is important to get it off as soon as possible. The longer the stain is left on the glass the more time it has to actually react with the glass and cause etching. Once glass is etched, it is difficult and time consuming to restore clarity. Full clarity may not be possible.
Removing hard water stains can be a real chore, and is usually not a pleasant task. Most window cleaners I know say they “hate water stain removal”. However, it does account for a significant amount of work for us, putting groceries on the table.
In the old days, window cleaners commonly used very harsh water stain removal chemicals containing hydrofluoric acid. Twenty years ago many window cleaning companies discontinued the use of hydrofluoric acid because it was revealed to be one of the most dangerous chemicals know to man. I do not recommend hydrofluoric acid to anyone for this reason.
One window cleaner I know told me a story of when he stored a little hydrofluoric acid in a coffee can over the weekend in his van. When he went to work on Monday morning, he discovered the bottom of the coffee can burnt completely through, then where the can was setting, the hole continued through the floor of his van. When he looked into the hole, he saw that the tail pipe was burnt completely through, then there was a white line on the concrete where the acid had run, followed by an 18 inch diameter circle of asphalt that had turned into gravel. My guess is that it is probably still burning a hole through the center of the earth and out the other side today.
There are safer products on the market today. Most of them seem to work ok on water stain that has not been on the glass for a long time. However, the longer the stain has been there, the more difficult it is to remove. I suggest trying a paste such as “A-Maze”. Put it on a white pad or a piece of “0000″ steel wool. Wear nitrile or neoprene gloves. If it does not work, you may have to resort to an electric polisher with a white pad. Put the past on the white pad and try polishing the water stain off. Remember to use safety glasses when polishing.
It is important to determine if the product you are using is compatible with the glass. I received a call one day from a homeowner whose windows had a cloudy appearance he after he used a water stain removal product on all of his brand new windows. The windows had been lightly water stained from sprinklers, and the product was applied without first testing for compatibility. Little did the homeowner know, there was a low-e coating on the outside of the glass that the product reacted with, producing very cloudy looking windows. I was later called to see if there was anything that could be done and was able eventually to restore clarity to the windows, but only by removing all the exterior low-e coating.
Water stain removal is not a fun job to say the least. Many professional window cleaners are prepared with other chemicals and techniques in their arsenal against water stain removal. We may not be able to always remove 100% of the stain, but most of the time we are able to get most of it off, to where what is left is hardly noticeable.