Windshield Sealant Vs. Windshield Adhesive
** Both Windshield Sealants and Windshield Adhesives are meant to fill in holes in the area surrounding your windshield or to replace them altogether. If you are looking for a way to fill a crack in your windshield, then check out our article on Repairing a Cracked Windshield. **
A windshield sealant is a glue-like substance that is used to fill in cracks or gaps between your windshield and the frame of your vehicle. These cracks can cause rains and other natural elements to leak into the interior of the car. This can cause damage and needs to be sealed off to be fixed. These sealants are flexible but do not have a lot of holding power as they are simply used to fill in gaps and plug holes.
A windshield adhesive is a special glue-like substance that is used to bond the glass to the frame of the car. Like a sealant, it needs to be durable to keep out the elements. And like a sealant, it needs to be flexible because cars flex when they move, and the adhesive needs to be able to absorb that flex so that the glass doesn’t break. Unlike a sealant, though, a windshield adhesive needs to have very strong holding power. It needs to create a permanent bond between the glass and the frame of the car. Most importantly, a bond that is strong enough to keep the glass attached even in the case of an accident.
Why Picking the Right Windshield Fix is Important
Windshield sealants work to fill in any gaps or cracks that have formed between your windshield and your car’s frame. This is usually noticed because water will begin to slip past the glass and frame and leak into your vehicle. This can be seen on any of your car’s windows or sunroof. And all of the products below can be used to fix any of these window leaks. When this happens, and water starts to get inside of your vehicle, you know it is time to reseal the window.
Windshield sealant works by filling in these gaps or cracks with a tough and durable like glue. This glue or sealant is weather-proofed against water and ice and can handle extreme temperatures. These windshield sealants are also shock resistant and chemical resistant. It is meant to last for many years, so it works extremely well to keep out the elements but also needs to be used with caution. Some of these products may require a caulk gun but will be noted as such if they do.
Types of Windshield Adhesive and Sealant
Butyl is a common sealant that was also used as a windshield adhesive back in the day. Butyl is a black tacky substance that works well to seal holes but doesn’t get used as a windshield adhesive anymore. That is because Butyl tends not to cure to a fully solid-state. This caused the windshield to have a very weak bond with the car so that during frontal collisions, the glass would actually eject out from the vehicle. Because of this, when adhering the windshield to the car today, manufacturers now use Urethane. Despite this, Butyl is still a good sealant and can be used to seal small holes. It holds up well against shock and temperature extremes.
Urethane is also a black substance, but it cures full and is flexible. Once Polyurethane is cured, it has a holding strength of 10,000 PSI. This is extremely strong and is more than enough to keep any windshield glued to the vehicle. Polyurethane also works so well as a windshield adhesive because it is flexible. When a car is cornering, it inevitably flexes, and you need a windshield adhesive that can absorb that flex so that the glass doesn’t break. Polyurethane is the perfect combination of both of these attributes.
Silicone is not often used as a windshield adhesive, but it does work extremely well as a windshield sealant. Filling small cracks or holes around the windshield and keeping out the elements. Silicone works so well because of its excellent flow. Once applied, it quickly slips down into small cracks and crevices to fill them and cures to create a strong but flexible seal. Silicone also holds up well against extreme weather conditions and ozone degradation.
Things to Factor in When Choosing Your Windshield Adhesive or Sealant
Prices can vary pretty significantly for windshield sealants, but like most things, you often get what you pay for. Make sure that you choose a sealant that will meet all of your requirements. Spending a little extra for a quality product now could save you from a larger bill down the road.
These sealants have to hold up against extreme temperatures, shock, water, and ozone degradation—more than likely, you are trying to seal a hole because your current windshield adhesive has already failed. So make sure that you get a windshield sealant that can hold up against these extremes.
Drying time is an important factor in picking a sealant. If you don’t have a way to cover your car from the elements, then choosing something with a faster drying time may reduce the likelihood of you getting caught in an unexpected storm. Any water and sometimes sunlight will ruin your sealant before it cures. Likewise, if you need an immediate fix and have to drive somewhere shortly, then check the packaging for its “SDAT.” This is the industry’s acronym for Safe Drive Away Time. Or the amount of time that your adhesive or sealant needs to cure before your car is deemed safe to drive.
If you are looking for something to bond your windshield to your car, then you need a strong but flexible adhesive. In this case, polyurethane would probably be your best bet. But if you’re looking for something to seal off a hole or crack on your existing adhesive. Then a light, flexible, natural flowing sealant would be the way to go. Silicone is usually your best bet to seal up small cracks around your windshield.
You also need to make sure that the style of the bottle matches your goal. If you are filling a small crack, then you don’t want a large tube that requires a caulk gun like you would if you were trying to adhere a brand new windshield. You also wouldn’t want a glue with a paintbrush if you are trying to fill a crack as you’d need a sealant with a nozzle and more flow so that it will penetrate deep into the crack.
Color is an important factor when picking out a windshield sealant. Polyurethane is black, so if your trying to fill in gaps on your own, then this is probably not your best option in case of an accident. Silicone, on the other hand, is clear. If filling in your existing sealant, then a clear drying silicone is your best bet, make sure you buy something of quality. Cheaper silicones say that they dry clear but will quickly yellow over time.
OUR FAVORITE WINDSHIELD ADHESIVES AND SEALANTS!
Best Windshield Adhesive
3M Window-Weld Super Fast Urethane is, without a doubt, the best DIY windshield adhesive on the market. This is a One-part urethane adhesive that requires no mixing, so everything you need is ready to go. It has a 10 to 20 minute work time, so it cures fast.
Its strong weld like hold will securely adhere your windshield to the frame of your car for a permanent bond. It is incredibly resistant to shock, extreme temperatures, rain, and ozone degradation, so you can expect this urethane to last the life of your car without a problem. This adhesive works with many materials. Some people have found it useful for adhering convertible tops back to their vehicle’s glass as well.
This product does require the purchase of a nozzle and a caulk gun. It will work with both manual and automatic caulk guns but for the sake of saving some money, we just recommend using the caulk gun recommended below, and don’t forget the 3M’s Threaded Cartridge Nozzles!
Best Windshield Sealant
The Permatex Flowable Silicone Windshield and Glass Sealant is the best DIY glass sealer on the market. You’ll notice that this sealant is much smaller than the adhesive and doesn’t require a caulk gun or an additional nozzle. That is because this is meant to fill in small cracks or gaps in your window’s existing adhesive.
This is a flowable silicone sealant that has a wicking action that Permatex says “seeks the leak” allowing it to naturally flow into small hard to reach areas. This sealant dries in about an hour and is fully cured in 24 hours. This sealant is extremely durable, shock resistant, chemical resistant and can handle extreme temperatures from -80 to 400 degrees Fahrenheit.
Best Non-Hardening Windshield Sealant
The 3M Auto Bedding and Glazing Compound is the perfect non-hardening window sealant to use as a supplementary sealer or as a fix to repair old or cracked window seals.
This compound is a non-hardening synthetic rubber-based formula and does require a caulk gun to use, but it doesn’t require any mixing, gives a 45 minute working time, and cleans up with a dry rag. This makes it one of the easiest non-hardening sealants to work with.
This bedding and glazing compound will never harden or crack. It is meant to be used between rubber windshield gasket and auto body, providing the ideal glass bedding surface. The non-sagging properties also make it excel when used on overhead and vertical auto seals.
Best Windshield Adhesive Tape
The 3M Windo-Weld Round Ribbon Sealer is the Best Windshield Adhesive tape out there. This tape has enough material for one windshield or backlight installation and is specifically designed to block light from the pinchweld. It also comes with a block setting to control the tape’s compressibility when installing the glass. Some people prefer to use tape because it is cleaner than liquid adhesive. The tape ensures that unlike liquid adhesive you can’t accidentally add too much where it spills out when set.
Best Windshield Urethane Adhesion Primer
This 3M Single Step Primer is the perfect way to ensure that your urethane adhesive creates a permanent bond with both the glass and the frame of your car. This is a super simple one-step primer that does require any activation and dries quickly. It protects your cars frame from corrosion and is great for touching up minor pinchweld scratches. It also protects the adhesive from UV damage for a long lifespan. This product works on both pre-applied adhesive (PAAS) systems or PVC/encapsulated glass.
Best Affordable Caulk Gun
Not only is the Newborn Caulking Gun affordable and reliable, but it works flawlessly with the sealants above. It has a steel half-barrel, also called a cradle, that is built to hold 1/10 gallon tubes like those above. It has a thrust ratio of 10:1, making it easy to use with low viscosity sealants. The rod has a smooth push, removing the bounce and noise that come with the typical ratchet style guns. The rod retracts after each pull of the trigger to avoid drips, and the handles are padded. What more could you ask for from a caulk gun?
How to Apply a Windshield Adhesive
- If necessary, using the appropriate tools, detach, and remove the old car windshield.
- Use 3M Adhesive Remover to remove any residue left on the glass or frame of the vehicle. This adhesive is safe for both glass and painted surfaces. Wipe area clean with a lint-free cloth.
- Once the glass and frame are clean, inspect the frame for any bare metal scratches. If there are any, they need to be scuffed and primed with 3M Single Step Primer.
- Now add your liquid adhesive or adhesive tape to the pinchweld on the car’s frame.
- Start at the bottom of the side pillar lining the adhesive up to the side of the pinchweld. If using the adhesive tape, make sure that you don’t overlap any pieces. Instead, butt the ends up against one another to form a tight seal.
- Now place the glass into the cars opening and push down with medium pressure to ensure a tight seal all the way around the glass.
- Wait for the sealant to fully cure, preferably overnight.
- Perform a water test to make sure that there are no leaks in the new windshield.
How to Apply a Windshield Sealant
- Perform a water test by letting a garden hose run over the windshield. This will help you identify the source of the leak.
- Once you have found the source of the leak, identify on the outside exactly what crack or gap needs to be filled.
- With painters tape, tape off the glass and paint around the area that needs to be filled. This will protect your car in the case of any accidents.
- Cut off the tip off of the windshield sealant and place the nozzle into the gap or crack that needs to be filled.
- Fill the problem area with windshield sealant until the sealant is level with the window and frame of the car. Remember, the sealant is supposed to leak into the cracks to fill them completely, so watch for settling as you are filling these gaps.
- If you overfill the area simply use your finger (with glove) to smooth out the sealant until the area is completely level
- Wait 10 minutes and remove the painters’ tape from the glass and paint. Don’t wait until the sealant is dried. If some sealant did spill over, then it will seal the tape to the car.
- Wait until the sealant is completely cured, preferably overnight.
- Try the water test again to make sure that you have taken care of the problem completely.