Basically, a window tint, or solar control film, is a very thin film usually made of a polyester base with a scratch-resistant coating. Some films involve multiple polyester layers to achieve their results. These films are still only millimeters thick and are affixed to the interior side of the window with an adhesive.
In order to create the sun barrier, manufacturers use different additives in special, usually patented formulations to create the desired characteristics. One type of film is dyed. This method for keeping the sunlight from affecting the interior environment of the home utilizes absorption of the sun's harmful rays. It should be noted that absorption of heat can increase the stress on the window's glass, which can periodically lead to glass breakage. According to the International Window Film Association's Web site, use of any window film will increase the thermal stress on sunlit glass [source: International Window Film Association]. For this reason, it's important to check the manufacturer's window restrictions before deciding on the appropriate film.
Two other types of window film work by reflecting a majority of the sun's harmful rays. One film is metalized, which means that the polyester base is embedded with different types of metals. The newest variety of film uses advanced ceramics to reflect sunlight.
Along with different methods for dealing with the sun, window films also come in many shades and colors. These can range from opaque to clear. Many of the tints available have a slight metallic look, such as bronze, stainless steel or gray. Some newer versions of window films are nearly clear. Along with style, color or shade can also offer other benefits. Tinted versions tend to offer more privacy, while the clearer films tend to be less reflective, giving less of a mirrored appearance in the evening.