How do I get streak free windows?

August 23, 2017 William Russell

Getting frustrated by streaks, smudges, and foggy glass? Here's the easiest way to get streak free glass.

The Science Behind Streaks

Ever wonder what is causing these ugly streaks and smudges in your glass? You wipe, and wipe, and wipe and just can't get them off. They move around, get worse after you think you removed them all, or you don't see them until you pull the car outside. The smudges in your glass can be removed, but we first should look at the science behind the streaks.

The vinyl and plastics used on vehicle interior panels contain plasticizers that help your interior remain flexible. This flexibility prevents interiors from cracking like they used to. When the interior panels vent, or out-gas, they release these plasticizers into the interior cabin of the car. Dioctyl Phthalate or DEHP, has been under recent scrutiny which led to the increase in use of diisononyl phthalate (DINP), diisodecyl phthalate (DIDP), and di(2-propylheptyl) phthalate. All of these types of phthalate will out-gas and cause streaking. They then get stuck onto the interior glass. It's always recommended to leave windows slightly open when possible. This will reduce the amount of built up plasticizers inside the cabin. Interior dressings tend to accelerate the out gassing and increase the buildup on the interior glass.

Best way to remove streaks?

Now that we know the cause, we can find the best method to removing the streaks and smudges.  As a detailer, we all know to first start with the least aggressive method and move on from there. As we are also now aware that it is the plasticizers causing the foggy glass, we should begin with a simple chemical cleaner. A glass cleaner of your choice will work best to start along with a lot of clean microfiber towels. I personally use Sprayway. It has strong chemical cleaners which helps a lot when it comes to plasticizer fogging.

  1. Spray your microfiber towel liberally with Sprayway (or cleaner of your choice)
  2. Wipe the glass in one direction. Move either left and right, or up and down.
  3. Use a different, but clean, Microfiber towel and wipe the glass in the opposite direction. If you wiped up and down with Sprayway, wipe left and right. Etc.
  4. Repeat the process again using more clean microfiber towels. Repeat steps 1 and 2.

The trick here is to not get too caught up and overwhelmed by the smudges. We are slowly removing the plastic residue from the glass. With each pass of a clean towel and Sprayway, we are removing a bit of the built-up plasticizers residue. The trick here is repetition and making sure you are always using clean and fresh towels.

Can I prevent streaking?

There are a handful ways to prevent the streaking, or at least reduce the buildup of plasticizers in your interior glass. One method is to thoroughly clean your interiors with water based cleaners. I prefer to do the occasional wipe down with warm water and a microfiber towel. Wipe down and remove any residual build up. The second method is to leave your windows slightly open whenever you have the opportunity. This has its drawbacks as you don't want dirt, water, or dust getting in. But it does help reduce the buildup on your interior. We also recommend against using any strong interior dressings which many times increase the out gassing of plasticizers.


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1 comment

  • Edgar

    Aug 23, 2017

    Thanks for taking the time to write this. Very informative.
    Will you please hit us up when your monthly box is back up and running?
    eAutomotiveGroup at gmail

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