Repcon was likely the very first hydrophobic sealant for glass developed in 1971. It was created specifically for aircraft. Rain X came out the next year in 1972. This was 54 years ago. Since that time there have been many different chemistries that were developed to accomplish a similar effect. It would not surprise me if there has not been well over a hundred different products put out on the open market. Most of which have claimed to be the very best. Many of these have been tested by accredited testing companies for things like hardness, rain repellancy, contact angle, scratch resistance, protection against hard water spots, longevity, ease of application, self assembling monolayer formation, and so on. With all of this confusion I don't think anyone could ever know the real truth about which one is indeed the absolute best. So I am not going to even attempt to answer that. But I will do something much better.
We can set up our own tests to determine which product we want to use. I have been doing this since 1985. Along the way I have discovered some fascinating truths. Which you can follow if you want to take the time.
The very first one that I would like to write about in this post is longevity. Using what I call field application testing. First find a single window that has full sun exposure. Meaning every square inch has the same sun exposure for the entire day. Then using a random oscillating polisher and a felt pad with some cerium, polish the window. Do a full polish and clean. Test to make sure pure water evenly sheets over the entire window. Meaning it is completely hydrophylic (water loving). Next apply the product you are testing to the entire window. Then tape some cardboard to half of the window. Give it a full month to bake in the sun. Now remove the cardboard. On a cool overcast day fog the entire window. This can be done with an cold ultrasonic fogger. Then take a handheld lighted microscope at 40X and look at the microdroplets on the fogged surface. The product protected under the cardboard should nut have been affected by the UVC of the sunlight at all. Those microdrops should be the same exact size they were a month ago. But if the side that was exposed to the burning sun had been degraded then those microdrops will be larger. The contact angle and hence the hydrophobic property will have changed. It should be quite apparent.
Using microdrops and a handheld lighted microscope is actually one of the most basic and very simple ways for testing other interesting properties of hydrophobic sealants/products. Solar UVC radiation is not the only means of hydrophobic degradation. Another is concrete deposits. As concrete cures it goes through a hightened pH at the glass concrete interface. Which can go as high as 9.5. At that number the sealant can completely break down leaving the phylic glass surface unprotected and exposed to attack by other construction chemistries. Hard water drops can also accomplish the same effect as they increase their pH as they evaporate and leave behind hard water spots. Using a light cerium oxide to remove secondary hard water spots will also degrade a phobic sealant/product. It should also be true that certain chemicals could also degrade phobic sealants.
But again the test is yours. You can even compare different products one to another to another over time for other properties. There really is no need to try to understand what certain test companies have discovered. We are the scientists. We are the technologists. We are the window cleaners. And it is our reputation that is on line. We must stand behind our work. Also we must demand top dollar for what we do. That takes confidence. Which also takes complete trust through private individual testing which we develop!
Written by Henry Grover Jr.
