We think that window film is great stuff. It can help to make your home more energy-efficient. Even the safest safety glass is safer with a layer of mylar on the inside, and window film also cuts down on sun-bleached carpets and drapes. Unfortunately, it doesn't last forever. You can, however, remove it yourself. And all it takes is an old spray bottle, a bottle of household ammonia, a roll of plastic food wrap and a putty knife. Put the straight ammonia into the spray bottle, spray it onto the window film and immediately cover the ammonia-wet area with a layer of plastic wrap. After 45 minutes, use a broad-bladed putty knife to remove the film. Make sure that the area is well ventilated and don't forget to use eye protection. Don't attempt the project on a real hot day. If the ammonia evaporates the technique won't work.