Guide to Glass Cleaning and Sealing

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Ultimate beginners guide to properly cleaning and treating automotive glass.

Glass cleaning is something I take pretty seriously. Not only do clean, spot free windows look awesome. They also increase the safety of driving your vehicle dramatically. This is a benefit to both you and everyone around you, a rarity in auto detailing.

Properly cleaned and treated windows will be crystal clear, almost invisible, even when driving in direct sunlight. They will also shed water better in the rain making it easier for you to see and reducing the work your wipers must do.

To top it off, perfectly clean glass, especially darkly tinted, ads a dramatic contrast to your car’s appearance. This is especially true for brightly colored cars like white and red. For black cars it seamlessly continues the deep wet gloss you work so hard to achieve on the paint.

That being said, to get perfect clean windows requires specific processes and quality products.

Glass Cleaners

Not all glass cleaners are created equal and some flat out shouldn’t be used for automotive glass cleaning.

Many glass cleaners contain ammonia and other solvents because they’re extremely effective cleaners (I’m looking at you Windex). The problem is these cleaners can damage materials on and in your car.

Ammonia, for instance, will degrade window tinting over time. It dissolves both the material in the film and the films adhesive. Ammonia also dries out plastic, rubber, vinyl, and leather. Always opt for ammonia-free cleaners. Avoid household cleaners because they almost certainly will contain ammonia or high levels of other solvents that will damage your car.

Another common problem with general glass cleaners is many of them contain waxes and other ingredients to try and increase the luster of the glass. The problem with this is that unless your windows are perfectly clean before introducing a wax or sealant you’re just going to mix in the dirt and create a hazy mess.

It’s also important that you do not use glass polishes on the tinted side of tinted windows. These polishes usually contain abrasives that will scratch the tint and citrus acids that will break the tint down.

Related: My Top 8 Best Glass Cleaners

Meguiar’s, Griot’s Garage, Stoner and many others make quality, safe glass cleaners worth your consideration. Fortunately for you getting clean windows isn’t as much about the cleaner you use as it the towels and techniques you use.

Glass Cleaning Towels

Choosing the right cleaning towel is the most important decision when trying to obtain perfectly clean windows yet it’s the most often overlooked.

The most common choice people make is paper towels or shop towels which are almost guaranteed to give poor results.

Paper towels are not only abrasive, but they also contain adhesives and dyes which are drawn out by glass cleaners and leave streaks on the glass. This is why you end up with streaks even after several cleaning passes. Paper towels also leave behind lint.

The best choice for cleaning windows is high quality microfiber towels. Quality microfiber towels are not abrasive, do not have adhesives dyes that leech out, and do not leave behind lint. Microfiber is also very good at absorbing, which is particularly important in the case of oils and other film on glass (those little smartphone cleaning cloths that magically soak up greasy finger prints are made of microfibers).

I recommend at minimum you acquire three dedicated glass cleaning towels, two general purpose waffle weave microfiber towels and one glass specific microfiber towel for the final wipe down. More on this in a bit.

How to Clean Car Windows – Cleaning Interior Glass

As stated earlier, when cleaning interior glass it’s important that you use a cleaner that is free of ammonia, especially if your windows are tinted. It will also benefit you to use three separate microfiber towels if you want a truly streak free finish, or what I call the “three-towel method.”

Always start your glass cleaning session in the shade with cool to the touch glass. Direct sunlight will evaporate the cleaner faster than you can buff it away and will leave streaks.

  1. Start by rolling your windows down a couple inches to expose the top of the glass that’s usually tucked into or against the seal on the door.
  2. Wipe down the seal with an all-purpose cleaner and a one of your non-glass towels. Over time residue and sealant can build up on the seals and transfer to your windows.
  3. Grab your first microfiber towel, fold it into fourths, and spray one side of it lightly with your glass cleaner of choice outside of the vehicle (to prevent overspray in the interior).
  4. Wipe down the glass thoroughly with the towel. Clean each area of the glass with multiple passes to make sure you don’t miss any areas.
  5. Take the second clean towel, fold it into fourths, and buff out the glass. I like to work up and down and back and forth across the entire glass to make sure I don’t miss any spots.
  6. Finally, take your glass specific towel and buff over the whole window to remove any last traces of cleaner, oils, or residue for a truly streak free finish.
  7. Roll you window all the way up and clean the bottom edge of the glass.
  8. Turn your towel to a clean side and move on to your next window.

The design of some cars makes it extremely difficult to clean the windshield or rear windows due to the angle of the glass and dash or rear deck.

One trick is to sit in the opposite side of the car you are trying to clean such as sitting in the passenger’s seat when trying to clean the driver’s side window.

Another trick is to stand outside the car with the door open or window rolled down and reach in.

If neither of those tricks will work for you then you can try a tool such as the Stoner Reach and Clean tool. If you use this I recommend purchasing an extra bonnet, so you can stick with our three-towel plan detailed above.

Dealing with Haze

There are many causes of the haze or fog that plagues most car windows. The materials that make up the interior, especially the dashboard, can out-gas when exposed to extreme sunlight and heat which leaves a film on the windshield.

Cheap interior protectants and dressings will also out-gas onto your windows.

The climate control system can also transfer moisture and other recirculated contaminants to the windshield when it blows on the glass.

The best way to prevent this haze is to park in the shade and use a quality sun shade. Purchasing a UV and heat blocking tint film also helps keep interior temps down.

Also avoid using cheap interior dressings, especially those containing silicones and solvents.

When possible, keep your climate control set to pull air in from the outside (turn off recirculate). This will prevent humidity increases in the car which begins fogging the windows.

I wish I could recommend a product you could apply to the glass to keep away fog and haziness but I’ve just never had any luck with the products that are out there.

As for cleaning haze, any quality glass cleaner should be able to cut through the haze using the three-towel method described above.

Dealing with Smoker’s Film

If you’re the unfortunate new owner of a car that was previously smoked in then my heart goes out to you. You have a serious uphill battle to restore your car from the damage that smoking does to interiors.

When it comes to removing smoker’s film from glass I recommend grabbing an extra sacrificial towel and using a strong glass cleaner such as Stoners Invisible Glass. Unfortunately, there is no substitute for hard work here. You’ll simply need to apply more elbow grease during the first cleaning pass with your sacrificial towel.

If the film is so bad that a glass cleaner cannot remove it you can try using a 50/50 mix of denatured alcohol and water or vinegar/water with a towel. Just be careful of your other interior surfaces. You may need to soak down the glass with this solution and let it dwell a bit before scrubbing.

I’ve even resorted to clay baring the glass (yes, just like you would your paint) with great success but you have to be sure to lay down towels to protect the interior from overspray and roll off of your lubricant.

How to Clean Car Windows – Cleaning Exterior Glass

Cleaning the exterior windows is similar to the interior windows unless you have water spots or etching. I recommend cleaning your exterior windows last to prevent contaminating them with any cleaners, waxes, or sealants you may apply to the rest of your vehicle.

If it has been a while since you’ve cleaned your exterior glass, you should consider clay barring them like you would your paint. Exterior glass is exposed to all the same problems such as road film, tar, tree sap, bugs, etc. Clay baring can help remove these and absolutely will not hurt the glass. Seriously, try it. You’ll be amazed.

After clay baring follow the same steps for the interior.

Dealing with Water Spots

To know how to deal with water spots you first have to understand what they are.

Water spots are dried mineral deposits and other dirt that are left after water air dries. Over time these spots can etch deep into the glass so it’s important to remove them asap and prevent them in the future.

A cheap home remedy that may work for removing water spots is regular household vinegar. Since the vinegar is acidic it will break down the minerals forming the spot and allow you wipe them away.

Tougher water spots may require a stronger cleaner that contains an abrasive such as Wolfgang Perfekt Vision Glass Polish. I’ve also had luck using the same compound I use for my paint to polish out glass to a spot free finish. Just make sure that once you use a buffing pad with a polish on your glass that you do not use it on your paint anymore.

Dealing with Etching

Etching is what happens when water spots, bugs, and bird droppings are left on a car for a long time and they actually eat into the glass. The only way you’re going to remove the visibility of these types of etching is to use a polish.

Illustration of etching in glass from the minerals in dried water spots and bird poop.

You may get away with using a glass polish by hand. If you do not, you can safely use an orbital polisher and a foam pad with a paint cutting compound to polish out the glass. Serious etching and scratching will require a glass specific polish and pad. This is a whole other topic on it’s own so I won’t get into the details here.

Sealing Glass

After cleaning your glass to a streak free shine you need to seal the deal with a quality water repellant on the outside glass. This will do two things, make it easier to clean and harder for contaminants to etch the glass and to help the glass shed water better during rain which will save both you and your wipers trouble.

You actually can use the same sealant you apply to your paint but they also make dedicated glass sealants/repellants. I’ve personally used and really like Griot’s Glass Sealant. It sheds water like Rain-X but isn’t as hard to buff to a haze free finish. It also lasts a good few weeks in occasional rainfall.

If you’ve never used a glass sealant I recommend you try it at least once. Once you see how little you need to rely on your wipers in the rain, and subsequently how much safer you’ll feel driving in the rain, I doubt you’ll stop using it.

Wipers

I want to finish with a quick note on wipers. For many people their wipers are a second (or third or fourth) thought when it comes to routine maintenance. It’s important you replace your wipers at least once a year to make sure they don’t break down.

Degraded wipers smear water and drag imbedded dirt across your class leading to streaks and scratches over time. This both looks terrible and reduces visibility making your car less safe.

I won’t get into what wipers you should buy but just about any new wiper is going to be better than old worn out ones. If you properly clean and seal your windows you won’t be as reliant the wipers anyway.

Alright, off my soapbox now.

Wrapping Up

To wrap things up, cleaning your windows both helps your car look its best and helps you see better. Using three clean microfiber towels and a quality ammonia glass cleaner will get you far. Finishing off with a quality sealant will help make your car safer and a true joy to drive.

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2 thoughts on “Guide to Glass Cleaning and Sealing

  1. Reply
    Charlie Bell - June 16, 2018

    This is a helpful summary, more informative and efficient than having to wade through tedious YouTube videos…

    Question: After sealing the glass with Rain-X or Griot’s, will using a cleaner like Stoner’s degrade the sealant quickly? After using a sealant, can I still clean the windows normally, regularly? Especially during bug season I like to clean the windows every couple of days.

    1. Reply
      Brian - June 16, 2018

      Thanks! Most glass cleaners contain alcohol which will work against the sealant over time in my experience. If you plan to use a glass cleaner frequently you’ll want to shorten your intervals between applying your sealant or pick up a glass cleaner that doesn’t contain alcohol like Shine Society or Adam’s Glass Cleaner.

      A quality car wash soap, on the other hand, won’t degrade it as fast and will typically be all you need to clean exterior glass that’s sealed/coated when washing the whole car.

      All of our cars have either a sealant or wax on them. I always wash the windows in the shade while washing the rest of the car and dry them first. I never have any issues with spotting or streaking so I rarely use glass cleaner on the exterior of my windows.

      Hope that helps!

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