Does Windshield Water Repellent Really Work?

NOTE: This is not new information, it stems from my readers wanting to know more about water repellents and a claim my car dealer made to me when he was trying to selling an additional feature.


If drivers are on the road long enough, chances of them getting caught in a rain is a very likely scenario. The driver may have the best wipers but still struggles to see through all the water on the windscreen.


To counter that problem, car manufacturers via their glass suppliers started offering water repelling windshield products such as Aquapel , but buyers complained that the price to get one cost way too much, roughly $50 USD. Competing products include PGW’s (formerly of PPG) Aquapel and Rain- X. Rain-X’s brand awareness in the automotive consumer product segment is particularly high, being claimed as second only to Windex.  Here are results of a test conducted in 2006, sample size unknown.  PPG Aquapel is usually used by service professionals rather than vehicle owners. PPG Aquapel isn’t as well-known as Rain- X. The results from the unofficial comparison test were surprising.  After having applied both products to separate sides of a car’s windshield, the technicians waited for rain and then taped the results at various stages, all the way from day one to day 72.  What we have learned is that both windshield treatments need speeds above 40 mph to whisk rain away effectively, but that the windshield wipers dramatically reduce the effectiveness of Rain-X over time, whereas the PPG Aquapel side was still effective after 60 days.

NOTE: These products were developed and offered to the car manufacturers as a possible product to eliminate the windshield wiper system, that never quite worked out.

Another Hydrophobic competitor on the market that has been making some pretty bold claims is Diamond Fusion. They claim, in tests that their product will achieve the following: Creates a surface that is 11.76 times more resistant to rock chips and pitting by reducing the co-efficient of friction on the surface of the glass – making the glass slippery.

  • Provides up to 20% more brilliance for increased visibility to extend driver reaction time.
  • The treated glass is easier to clean and maintain. Insects, snow and ice are easily removed or washed away.
  • Gives drivers a 30% reduction in night-time glare by improving the optical clarity and reducing the prism effect.
  • Provides an unprecedented hydrophobic property which causes a water repellent.

“Creates a surface that is 11.76 times more resistant to rock chips and pitting by reducing the co-efficient of friction on the surface of the glass – making the glass slippery”

This is a statement that can be construed inaccurately or even wrong and misleading. Read it carefully. …”11.76 times more resistant” My car dealer (business office) trying to sell this product to me as an add on @ ~$14.00/month, told it would make my windshield ‘stronger’. I am a glass (ceramics) engineer, I know what will make my windshield stronger and what won’t. It may make the windshield more resistant to stone chips by that amount, (I haven’t done the math) due to a reduced co-efficient of friction,  but it won’t change the molecular field of compression and tension (which is where glass fails).

Hydrophobic Coating versus No Coating

The glass panel on the left has been treated with the hydrophobic coating Diamond-Fusion, causing the water to bead up. When tipped vertically, a portion of the water on the untreated panel at right would drip off, but much would stay on the glass, depositing its mineral content and creating “hard water” stains. The water bead on the treated left would quickly roll off the glass leaving little or no water to stain.

Both types of coatings fill in the microscopic peaks and valleys present in virtually every glass surface, resulting in a smoother surface. That is where the similarity ends.

Hydrophobic coatings create a surface that repels water. Supporters claim that by repelling water and the minerals it carries, fewer drops can stick to and dry on the glass, resulting in fewer spots. When it comes time to clean the glass, those spots can’t stick as easily to the smooth surface and are easier to remove.

Hydrophilic coatings create a surface that attracts water. Supporters claim that by attracting water, it sheets off and carries away any loose materials. The remaining water that sticks to the glass is spread out, so it deposits the mineral content broadly, and staining isn’t immediately noticeable.

Proponents of both coatings agree on the main benefit they provide: Consumers have to clean less often to maintain the beauty of their vehicles.


Now, the most often used solution to this problem is to manually apply water repellent products that are rubbed onto the windscreen to improve visibility.

However, does this product really work, it will be very frustrating to go through all the trouble of putting it on only to find out it doesn’t work. It does, the products basically repels the water and snow from the surface of the windscreen. When applying, the chemical will bond with the windscreen to increase the water repellency of the windscreen. Results prove that the product repels rain and snow. Some even reduce glare. It does not as some dealers say; increase the strength of the windshield.

But there is a downside to this as well; some products might damage the paint of the car if applied on the paint. Some products that use oil will also wiper degradation. There are now biodegradable products that won’t damage the wiper and has no toxic in it.

As for how long it is going to last, it depends on the product. Some can go on for month while some disappear in weeks. There are also method online that teaches car owners how to make some at home, but those probably won’t as long as the chemical laden stuff.




One response to “Does Windshield Water Repellent Really Work?

  1. Our Rainmagic treatment is the only water based environmentally safe product tested safe for motorcycle and auto windshields by G.E. and will last for up to one year without reapplication and has been used by major race teams since 1995
    Rrainmagic one year youtube demo

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