Anti-Frost Spray? Yeh right

Well the other day I bought a spray bottle of an Anti-frosting agent, it claimed that if you sprayed the car windscreen the right before a frost it would not frost over. So night one a few liberal spays as per instructions, next morning car frozen solid.

Ok I thought maybe I used to little or the frost was to hard? So last night I went to town, using almost half the bottel and well here is the results. Still frozen over. Ok it was a little easyer to scrape, but only a little and certainly nor worth the effort or expence.