Now as time passes the spots will become heavier. Then they will become visible in the direct sunlight. As more time passes they will become much easier to see. Even on cloudy days. Then they will become heavier and heavier until they are like braille. If they were removed when they first showed up, and the glass was sealed with a quality sealant, the windows could be effectively maintained at a reasonable cost. But if allowed to get really thick extreme measures will be needed to "restore" the windows to original clarity.
Each new spot usually forms directly on top of the previous spot. This is because dry spots catch water drops. Which drops will dry in the sunlight. As water drops dry/evaporate the minerals become more concentrated. All drops dry from the middle out. Such that the outer edge becomes loaded with mineral deposits. The outermost region of each spot has the most minerals. This is also the part of the drop that attains the highest pH just before all of the water evaporates. It is the area where a dynamic stage two etch is most likely to happen. Owing to the very high pH. This can actually be seen sometimes as a clear distortion of the glass when it has been polished. The clear distortions will take on the exact shape of each spot. This is not theory. I have proven it on a piece of dark glass. Dark tinted glass is more easily etched by hard water. It is also the most difficult to restore. Transparent glass is easier to clear. Then low e windows that have been coated on the first surface/weather surface are the easiest to restore. Low e coatings can be damaged also by hard water spots. These coatings are very thin. So the mineral deposits can literally eat right through them.
The bottom line here is to only hire a window cleaning company that is Glass Smart. They must be spot wise. Hard water spots can come from the garden hose, sprinkler systems, concrete, brickwork, exterior stucco, and more. Once they begin your window cleaner should recognize them. They should be immediately removed and the glass sealed. Then the windows should be cleaned again in six months. The sealant should be checked and any new spots should be removed. At this point it will be much easier to remove new spots and rejuvenate the sealant.
Hard Water Spots can be quite destructive. If allowed to build up to a thick scale the cost to renew or restore the glass to the original clarity can cost as much as one quarter the cost of replacement. Not to mention the cost of restoring any anodized aluminum frames.
Written by Henry Grover Jr.
henrygroverjr@gmail.com
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