The Best Windshield Water Repellents [2023]

Why You Should Use a Windshield Water Repellent

As a driver, visibility is crucial for your safety on the road, especially during rainy or snowy weather. Windshield water repellents can help you achieve better visibility by creating a hydrophobic coating that repels water, snow, and ice. In this article, we’ll dive into the science behind how these water repellents work and the advantages they offer. We’ll also highlight some of the best options on the market and guide you through the pre-application process.

How Windshield Water Repellents Work: The Science Behind Hydrophobic Coatings

To understand how water repellents work, you first have to understand the science behind what makes an object hydrophobic or “afraid of water.”

Glass is made of silicon and oxygen atoms with an occasional exposed “OH” or “hydroxyl group”. This hydroxyl group has a strong polarity because oxygen is electronegative. This polarity is similar to that of water, making the water chemically attracted to the glass. This attraction is why water doesn’t naturally roll off of glass.

So, in order to make glass hydrophobic, you need to reduce its polarity. This is where a windshield water repellent comes in. These products are non-polar. This non-polarity is often achieved using a chemical called PDMS. PDMS is a polymer made up of silicon, oxygen, and carbon-containing methyl groups. For a simpler explanation, PDMS is similar to oil, and as we know, oil and water don’t mix.

The second most common chemical structure in water repellents is “fluoroalkylsilane,” or “FAS”. This is made with a long chain of carbon and fluorine atoms, and similarly to PDMS, it is non-polar.

When water hits untreated glass, the polar attraction causes it to flatten out and stick to that glass. Once you treat this same glass with a hydrophobic polymer, like PDMS or FAS, the glass becomes hydrophobic. These hydrophobic properties cause that same water droplet to ball up into a tight sphere. This reduces the surface area of the water touching the glass, allowing it to roll off easily.

The surface area of the water touching the glass is also known as the contact angle. You will often hear people say that these windshield water repellents will increase the surface angle of the water that sits on your glass. While some talk about the surface angle, the contact angle is the true measure of a chemical’s hydrophobic nature.

Knowing the contact angle will tell you how easily the water will slide off the glass. A higher contact angle means better water shedding.

PDMS vs FAS: Choosing the Right Water Repellent for You

When it comes to choosing a windshield water repellent, it’s important to consider the difference between PDMS and FAS polymers. While PDMS polymers like Rain-X have a higher water-shedding ability, they cannot chemically bond with the glass. This means that they are better at getting water off of your windshield, but they are more susceptible to erosion from external factors like friction from windshield wipers, UV rays, and extreme temperatures.

On the other hand, FAS polymers like Aquapel chemically bond with your glass, allowing them to last an extremely long time. However, the process used to create this bond diminishes its ability to shed water, meaning they don’t work quite as well as PDMS polymers at repelling water.

Ultimately, the choice between PDMS and FAS comes down to what is most important to you in a glass water repellent. If extreme contact angle and water-shedding abilities are your top priority, then a PDMS polymer like Rain-X may be the best choice for you. However, if you’re looking for a longer-lasting option and don’t mind sacrificing a bit of water-shedding performance, then an FAS polymer like Aquapel may be the better choice. It’s important to weigh the pros and cons of each option before making a decision.

If you’re looking for something that will last as long as possible, you may also enjoy our article on glass sealants.

Benefits of Using a Glass Water Repellent

Increased Visibility

A windshield water repellent will greatly increase visibility in a rainstorm. Water repellents are hydrophobic, causing water to form tiny droplets when they hit the glass. These droplets are much easier to see through than a sheet of running water. These tiny droplets will also roll off the glass at speeds as low as 25 mph, allowing you to see clearly without the need for windshield wipers.

Better Reaction Times

Since these hydrophobic coatings increase visibility, the Transportation Research Institute decided to research how that affected a driver’s reaction time. They found that when a hydrophobic coating was applied, it increased the driver’s response time by 25%. This increase could potentially make the difference between getting in a serious accident and reacting fast enough to avoid one.

Repels Water, Snow, and Ice

Just like it does for rain, a coating of windshield water repellent will also repel snow and ice. This increases visibility as snow will not be able to stick to the windshield. These hydrophobic coatings resist frost as well, shortening the amount of time it takes to clear your windows in the morning.

Less Hard Water Spots

Hard water spots are the bane of every car owner. They decrease the visibility of your glass, they look bad, and they are extremely hard to remove. But just like a good coat of wax protects your paint, a good coating of water repellent will greatly reduce the amount of hard water that can stick to your glass.

Easier to Remove Bug Splatter

As gross as it is to think about, just as water repellents seal the glass from water and snow, they also seal the glass from bug guts. You may still get bugs stuck to the glass, but it will be much easier when you go to remove them. No more scrubbing and scraping, trying to get them all off.

Less Need for Windshield Wipers

Not only will a windshield water repellent decrease the number of times you have to engage your windshield wipers. It will also increase how smoothly they slide across the glass. This reduction in friction will increase a windshield wiper’s lifespan.

OUR FAVORITE WINDSHIELD WATER REPELLENTS!

Best Overall

Rain-X is a reliable and cost-effective option for windshield water repellent. Its proven track record in the market makes it a favorite among car owners. The application process is easy and quick, and it provides excellent results. Rain-X was originally designed for fighter jets, which means it has undergone thorough research and development. Although it may not last as long as other products, it still offers a reasonable lifespan. Rain-X is a brand that car owners can trust, and it is a product that I personally keep at home.

Pro Tip: Don’t apply Rain-X windshield water repellent after you’ve washed your car. This will leave a haze on the windows that can take forever to get off. Ensure that the glass is clean but apply Rain-X before you wash the car. Then when you spray it with water, the haze will just wash away. When you go to dry the car after it’s been washed, dry the windows as well. Now you are left with clean, streak-free windows and a fresh coat of Rain-X windshield water repellent.

Quickest Application

In search of the easiest windshield water repellent? Look no further than Invisible Glass Clean and Repel! This 2-in-1 glass cleaner and water repellent works like a charm, getting the dirt and debris off your windshield while applying a water repellent coating that’s just as effective as Rain-X. Unlike Rain-X, there’s no need for multiple coats or to buff out a haze once it’s dried. Simply spray, wipe, and you’re done!

While Invisible Glass Clean and Repel doesn’t last quite as long as Rain-X, with a lifespan of about two or three weeks, it’s perfect for those who clean their car every week anyway. And the best part? You don’t need to thoroughly clean your windshield before applying it, making it a much less tedious chore than applying Rain-X. So, if you’re looking for a hassle-free, effective solution to keep your windshield water-repellent, Invisible Glass Clean and Repel is the way to go!

Longest Lasting

There are a lot of smaller, high-end brands producing windshield water repellents, but only Gtechniq G1 seems to have really gotten it right. Gtechniq is a highly respected brand in the car care market that has made its name creating a lot of new nanotech car care products. Gtechniq’s G1 is an ultra long-lasting film that chemically bonds to the car’s windshield, creating a hydrophobic surface that is said to last up to two years. However, anecdotal evidence appears to suggest that its water repellent properties last about one year.

On top of being a good water repellent, the hydrophobic coating also makes removing things like bugs and dirtier easier. 

While G1 is extremely long-lasting, Gtechniq is honest in mentioning that there is a trade-off between longevity and effectiveness when creating these formulas. Gtechniq admits that by making their G1 product last so long, it did lose some of its water-shedding properties. So if you want maximum water repellency but diminished product life, they point you to their Gtechniq G5. This only lasts 3 to 6 months but is more effective at shedding water, especially at lower speeds.

Before Use: Before applying anything to your windows, make sure that you check out our article on the best car window cleaners. Using these products will ensure that your windshield is free of any contaminants before application. This will help your water repellent coating to go on properly and lasts longer!

Honorable Mention

Aquapel comes from the makers of PPG, the industry leaders in glass technology. Like Rain-X, this was originally created for the Aviation Industry. And like Gtechniq, it is able to chemically bond to the windshield, which allows its water repellent properties to last much longer than most of its competitors. Under everyday driving conditions, they say Aquapel should be able to last 4 to 6 months.

This product is a little bit more expensive than the others, but it lasts longer than Rain-X and is much easier to put on than G1, so it falls somewhere in the middle. Nonetheless, it is getting an honorable mention because it is a good windshield water repellent and does tout a pretty long lifespan.

What to Do Before You Apply Your Windshield Water Repellent

Before you apply any water repellent coating, you need to make sure that your windshield is clean and free of any contaminants. To do this, we recommend using Invisible Glass Premium Glass Cleaner to get off any of the big stuff. Then, continue with Griots Garage Glass Cleaning Clay and Griot’s Garage Speed Shine as a lubricant.

After using the clay bar, you may need to polish your windshield. Do this step if your glass has scratches, etching, or other imperfections. It is important to use the clay bar before the polish because you don’t want to drag debris across the glass and scratch it while you are polishing. It is also essential to use an extremely fine polish on the glass.

We recommend Griot’s Garage Fine Glass Polish. They recommend you use a random orbital for maximum efficiency. The Dewalt Cordless Variable Speed Rotary Polisher Kit is a good one because the cordless design makes it very easy to use around the car. But honestly, if you don’t want to buy an orbital doing it by hand will work 90% of the time. This polishing step ensures that your windshield water repellent will adhere better to that glass, allowing it to stay on longer and work more efficiently.

Once you have polished the car, clean it one more time with the Invisible Glass Premium Glass Cleaner. Make sure that you use two microfiber cloths when doing this. The first microfiber cloth will be used to wipe off anything leftover on the glass. The second microfiber will be used to dry any remaining cleaner. Once you have done this, you are all set and ready to apply your windshield water repellent.