Some windows aren't glass at all, but acrylic. I would hate to have to go through THAT!
I've heard acrylic windows burn if you squirt lighter fluid on them, then strike a match. Don't know if it's true. In no event would I try it from inside the room! :-)
I heard that movie windows are made from sugar -- nothing is what it seems to be...
Here's the recipe:
http://www.geocities.com/Hollywood/Lot/9373/SCREAM/glass.htmlKeeping it frozen extends the life of the pane if you need to store it for more than a few hours. (There are molds to make sugar glass bottles that you see breaking over people's heads in TV bar brawls.)