Hard water deposits are not only a nuisance but can eventually lead to damaged windows. Hard water deposits are derived from water that contains a high mineral content. This type of water usually consists of magnesium and calcium along with other compounds.
These mineral compounds are collected and dissolved into the water as it passes through the ground. The problem is that the hard water will evaporate from a surface such as a wall or window, leaving behind its unwanted deposits that are known as calcium or lime scale. You may not even notice the deposits starting to build and might just put it off as a dirty window.
If unnoticed, these deposits will start to build into a thick white layer of crust. As the build-up continues, it will give your windows an undesirable hazy, bullet-proof texture. Mineral deposits are fairly easy to remove during the beginning stages, but over time the deposits will slowly etch into the pores of the glass and can become baked on by the hot sun.
Once this happens, it can be virtually impossible to remove the deposits without damaging the surface that it’s adhered to.
This stage usually happens when hard water has been sprayed onto a window once or twice with ground water from a sprinkler or garden hose. After the water has evaporated, visible spots are left behind. These spots can usually be removed with regular window scrubbing tools along with normal scrubbing methods.
At this stage the mineral deposit has started to build up to the point where it has a somewhat transparent, but white pasty look. At this point, it may be difficult (but not impossible) to remove with normal scrubbing. A window scraper and acid base or light abrasive glass cleaner will work like magic to remove the water spots.
This is where the hard water deposits have built up to the point where they have etched into the pores of the glass. As you can see from the picture, the scale has not only damaged the glass but has damaged the frame as well. You will see this a lot of times on shower glass and doors along with lower outside windows that have been hit over and over by sprinkler systems. You will know the damage has been done when the window scraper or cleaners will not remove the scale build-up, no matter how hard you try. At this point, the window will have to be buffed out by using a special buffer, along with abrasive window buffing pads.