Re: How does a de-icer for windshields work?

There are two kinds of de-icers. On car windshields, a very thin layer of 
metal is deposited onto the glass during manufacture. Electric contacts are 
connected to each side of the windshield, and a current passes through this 
metallic layer, which raises the temperature high enough to melt frost. It's 
just like rear window defrosters, except the metallic layer is much thinner 
(so you can see through it) and uniform across the glass (so no bands 
appear). The second kind of de-icer is chemical. It's not used in cars, 
because it's fairly nasty to the environment, but is frequently used to de-
ice airplane surfaces. There is a third kind of de-icer which most people 
are forced to use, which involves muscle power. It's called an ice scraper. 
(Credit cards work pretty well for that job, by the way!)