Is Ammonia-Based Glass Cleaner Bad for Your Windshield?

Little girl washing car window, view from inside

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A popular misconception in the world of auto repair and maintenance is the belief that Windex and other glass cleaners containing ammonia are bad for car windshields, as well as side-view and rear-view car windows. Some people believe that the ammonia in these cleaners, while they may serve as a good disinfectant and degreaser, can "dry out" or discolor glass surfaces. There are a number of errors in this very common belief.​

Is Ammonia Bad for Auto Glass?

In reality, auto shops and auto-glass replacement vendors report no such problems with auto glass that has been cleaned routinely with ordinary household glass cleaners containing ammonia. It should be remembered that glass is one of the most impervious man-made materials available. Long before plastics were available, glass was used to hold everything from daily milk deliveries to the research scientist's hydrochloric acid in laboratory experiments. Glass holds pretty much all liquids just fine without degrading them in any way. You would be hard-pressed to come up with any liquid at all that will seriously affect glass. 

While automobile windshield glass is constructed with a lamination process that bonds separate layers to a vinyl center layer in order to make the windshield shatter resistant, the outer surfaces are still plain old-fashioned glass, and they can be cleaned just like any other glass surfaces in your home. Nor does tinted glass have any restrictions on how to clean it—except that it's usually recommended to clean with a very soft cloth if the windows were treated with an after-market tinting. But with factory-tinted car windows, you can clean away to your heart's content. 

How About Other Materials in Your Car?

To take the question further, we might also ask about what effect ammonia-based glass cleaner will have on other surfaces. Very close to the glass in your car windows there are rubber or vinyl seals, paint, and chrome trim. And inside the car, you likely have leather, vinyl, all sorts of plastics, and maybe even wood. Through long experience, car care specialists have found that ammonia may hurt very, very old paint jobs if they have already severely dried out. But even fairly worn rubber and metal trim does not seem to suffer at all from the contact with ammonia cleaners. Your windshield wipers, too, will largely be unaffected by glass cleaners, unless they are already so old they are on the verge of disintegration anyway. 

Inside the car, you should keep the glass cleaner away from your leather interior pieces. There are some excellent leather products for car seats that will make your leather last forever, but glass cleaner isn't one of them. Ammonia-water cleaning solutions are more likely to dry out or discolor fine leathers than they are to clean them. 

Did You Know?

Ammonia-based glass cleaners are routinely used as disinfectant cleaners, but in reality, glass cleaners like Windex are not very good at disinfecting. Although household glass cleaners may knock out a number of germs, serious bacteria such streptococcus (the bacteria responsible for infections like strep throat) are not killed by glass cleaner.

If your goal is to rid surfaces of serious bacteria, a cleaner based on chlorine bleach, such as Clorox foaming bathroom cleaner, will do a much better job than ammonia-based glass cleaner.