I often get asked by customers what I think about using "Windex" (or other ammonia/ammonium hydroxide based cleaners) on windows and mirrors. Which is a loaded question for window cleaners. Bottom-line, we window cleaners HATE these products. If a "professional" window cleaner shows up with Windex and newspapers in-hand, they probably think a Squeegee is a type of Pokemon. The reason for the hatred of this inanimate liquid is that when these products evaporate, they leave a residue that over time becomes a film on the surface of your glass. Have you ever cleaned and cleaned and cleaned a mirror but it still looked hazy? Evil Windex film.
That being said, there is a place for Windex to live harmoniously with your window cleaner and his disdainful opinions of the blue scourge. As we professionally clean your windows, we remove that film for you. Meaning that you can go about breaking our hearts by using Windex to your heart's content between cleanings and your windows will still look great! That's because you will be using the product as it should be used: As maintenance, not as a cleaner.
So, is Windex evil? Yes. However, if used in conjunction with a regular professional cleaning schedule, it's more like a Scooby-Doo villain evil. We can live with that.