I decided to clay my van's windshield today. The windshield is only a year and a half old, but it got to the point where Invisible Glass cleaner still left behind some 'junk'. I cleaned it as good as I could with the Invisible Glass, then clayed the windshield one half at a time, using straight water as a lubricant (normally MeGuiar's regular Quik Detailer is my go-to, but it creates a beading effect, which I don't want on the glass). When done, wipe dry, then clean once more with your glass cleaner of choice. It's much smoother to the touch now. I even noticed that now the glass cleaner comes away easier while wiping. Even if your vehicle/windshield is relatively new, I highly recommend doing this.