How do I clean windows without streaking?

Cleaning windows is one of the most irritating parts of detailing cars.  It doesn't matter if you have been detailing for 1 day or 20 years.  Many detailers will tell you the same thing--cleaning windows is the worst.

The most important thing to remember when cleaning windows is the golden rule of detailing: if it doesn't look clean, it isn't. That being said, here are a couple of tips that will help you to get those windows clean.

Chemicals

The key ingrediant to many window cleaners is ammonia.  The cleaner that we like best is Zep formula 40 or Zep 40.  We get it in cases directly from the manufacturer.  We have found that this glass cleaner has a very wide variety of uses.  In addition to cleaning windows well, it is GREAT for cleaning headliners (although leather cleaner is cheaper and works almost as well).  

You have to be careful with Ammonia based window cleaners.  They have a tendancy to destroy tint (especially older cheap tint), but for the most part they are the way to go when cleaning windows.  You should always use a light application of window cleaner when cleaning windows.  The more product use, the more residual you will leave on the window, and this is what will cause streaking.

Wet side/dry side

When cleaning windows it is best to use a dry micro-fibre towel.  Fold the towel into quarters so that it is a small square.  One side is your "wet side" and the other is your "dry side."  Apply a light mist of window cleaner to the window and wipe with the wet side.  Once you have cleaned whatever fallout or dirt is on the window, flip the towel over and use the dry side to wipe the residual liquid from the window.  This is how you prevent your streaks.

When you are cleaning the window with the wet side, make sure and clean the edges of the window thoroughly.  The best way to do this is to feel the window edges through the towel with your finger tips.  Press firmly so that you will get all the way to the edge.  Don't forget to role down the window a little first so that you can clean the top edge where the window meets the top of the door (many customer check this spot as a sign of a "good" detail).

When the chemicals aren't enough

Sometimes there is material on the window that refuses to come off like some type of adhesive, sticker, or other fallout.  The best way to get this off is to apply glass cleaner and scrape off with a fresh razor blade.  Be careful with the corners of the blade so as not to scrape the window.

If that doesn't work, mildly abrasive steel wool will.  Again, be careful not to scrape to hard.  You shouldn't have to scrape to hard to get any type of fallout off.

For information on how to remove water spots from the windows of your car please see the article on water spot removal.