# What is the purpose of this window-edge pattern? **URL:** \ **Category:** Factual Questions\ **Created:** [September 6, 2015, 2:31am UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-this-window-edge-pattern/730139 "2015-09-06T02:31:17Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![Sunspace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sunspace/32/1250_2.png) [@Sunspace](https://boards.straightdope.com/u/Sunspace)\ **Post date:** [September 6, 2015, 2:31am UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-this-window-edge-pattern/730139/1 "2015-09-06T02:31:17Z")
I’m on the top deck of a bus heading for Peterborough, Ontario. Around me are windows with a curious pattern around the edges. The pattern is a gradient made of differing-size black dots, so that there is almost a transition between opaque and transparent. [Link to phone pic.](https://www.flickr.com/gp/komiksulo/j41m5W) Does this serve any purpose other than decoration? ---
**Author:** ![Amateur\_Barbarian](https://avatars.discourse-cdn.com/v4/letter/a/59ef9b/32.png) [@Amateur\_Barbarian](https://boards.straightdope.com/u/Amateur_Barbarian)\ **Post date:** [September 6, 2015, 2:52am UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-this-window-edge-pattern/730139/2 "2015-09-06T02:52:21Z")
I believe it helps smooth the visual transition from glass to body from the outside, giving the bus a “softer” look. Quite a few cars use the same blending technique to keep the transition from body to glass from being so stark. ---
**Author:** ![SigMan](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@SigMan](https://boards.straightdope.com/u/SigMan)\ **Post date:** [September 6, 2015, 3:05am UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-this-window-edge-pattern/730139/3 "2015-09-06T03:05:23Z")
I notice that on my car. I think that’s the best explanation you’ve made. It’s to subdue the contrast where it’s not noticeable. ---
**Author:** ![GaryM](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/garym/32/241_2.png) [@GaryM](https://boards.straightdope.com/u/GaryM)\ **Post date:** [September 6, 2015, 3:09am UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-this-window-edge-pattern/730139/4 "2015-09-06T03:09:11Z")
It also serves as a primer when the glass is glued to the body. They don’t use rubber molding and trim strips anymore. Glass is glued in. I don’t have a cite, but I believe that’s it’s main purpose. Also hides the glued area from view. Here’s a cite: [The Purpose of the Frit (Black Band) and Spots on Windshield - DeDona Tint & Sound](http://www.dedona.com/the-purpose-of-the-frit-black-band-and-spots-on-windshield/) ---
**Author:** ![Fubaya](https://avatars.discourse-cdn.com/v4/letter/f/c2a13f/32.png) [@Fubaya](https://boards.straightdope.com/u/Fubaya)\ **Post date:** [September 6, 2015, 3:11am UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-this-window-edge-pattern/730139/5 "2015-09-06T03:11:42Z")
It’s not the body to glass transition, it’s the transition between the glass and black band at the edge. That edge is called the “frit” and is made into the glass to give the urethane adhesive something to stick to. ---
**Author:** ![Sunspace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sunspace/32/1250_2.png) [@Sunspace](https://boards.straightdope.com/u/Sunspace)\ **Post date:** [September 6, 2015, 3:18am UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-this-window-edge-pattern/730139/6 "2015-09-06T03:18:08Z")
Windows are _glued_ in?!! How does that work? Most of the windows on these buses are frameless, I think… but I’m not certain. I’m pretty certain that the emergency exit windows have frames. Is some sort of attachment hardware glued to the inside of the window? ---
**Author:** ![bob\_2](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bob_2/32/3341_2.png) [@bob\_2](https://boards.straightdope.com/u/bob_2)\ **Post date:** [September 6, 2015, 9:25am UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-this-window-edge-pattern/730139/7 "2015-09-06T09:25:36Z")
Windows in vehicles are now part of the structure. They are bonded into the frame and become integral with it, thus reducing the amount of metal in the construction. It also looks better and is more aerodynamic. If you need a replacement windscreen these days, you have to wait at least an hour, and preferably a lot more, for the cement to set before driving off.