Translucent windows allow light in but don't offer a clear view of the contents (or people) inside. Applying a film over windows is an inexpensive way to get the translucency that safety experts advise for windows in your basement and elsewhere that you don't want a would-be thief to be able to see through. In fact, for hard-to-fit windows of any kind, a translucent film over the window can be an attractive substitute for curtains or blinds as well as for frosted or etched glass.
Choosing a Film
Hardware stores typically offer window frosting by three methods: spray, vinyl film with adhesive and vinyl film that adheres through static electricity.
Of the three methods, frosting spray is the cheapest and easiest to apply--and the hardest to apply evenly or to remove. If you have many windows to frost and you don't care how they look, this method may work for you. It's quick; there's no cutting or fitting. But if you ever want to remove a blotchy sprayed coating, you will curse the person who sprayed frosting on your windows, even if you did it yourself.
Vinyl Film With Adhesive
Vinyl film with adhesive is more expensive than spray and less expensive than nonadhesive vinyl. It is the most difficult to apply, but if applied carefully it can provide a good coating. It is easier to remove than spray but is not reusable like nonadhesive film. The film is thinner than static-applied vinyl and usually comes in a kit with spray bottles of proprietary adhesive and adhesive remover. Often the kit will contain a plastic straight-edge/squeegee for smoothing out bubbles and a razor knife for cutting. Apply it carefully, because once it's on, it's on to stay. Smooth out bubbles and wrinkles while the film is still wet. Follow the directions to cut a piece larger than the window and trim after installing, because if you notice gaps or crookedness after it dries, you start all over. Removal of the film requires adhesive removal as well.
Vinyl Film Without Adhesive
This type of film is only slightly less difficult to apply than spray and has many advantages. But nonadhesive window film is the most expensive of the three, costing two to five times more than the other methods, depending on the pattern. Nonadhesive film is cut to fit and is applied wet, just like adhesive film. But it is removable and reusable. It comes off the window with no permanent marks, and if you discover a bubble or wrinkle or crooked edge after it dries, it's no problem to pull it off and try again. Nonadhesive vinyl comes in translucent frosting, just like the other methods, but it also comes in many (more expensive) patterns that mimic pricey etched or stained glass.