Creating a "frosted" effect on windows can offer any room in a house or office a new look. The "frost" look is also commonly used to increase the privacy within a room. Despite the usual implementation of this effect on glass, it can also be used on plastic surfaces by various methods, both temporary and permanent. Just decide which method is best for your purposes and start frosting.
Clean the plastic surface with a mild soap and water to prepare it for effective coverage of the frost spray. If possible, lay the plastic sheet on a flat surface. Once clean, spray on the frost. There are "frost" spray paints, such as "Rust-Oleum's Frosted Glass Spray" that can also be used on plastic surfaces. Spray a quick and even coat across the plastic and let dry for at least 48 hours before moving.
Lay plastic horizontally in an open space if sanding the material. Use fine sandpaper on a sand block or a fine-sand blaster on the plastic to achieve a smooth frosted appearance without deep scratches. Be sure to evenly sand all parts of the surface for a consistent frosted effect.
Apply frosted sticker sheets (found in some craft stores). Cut the sheets to size before applying. When attaching the sticker to the windows, be sure not to touch the adhesive side, as it can ruin in the integrity of the product. Line up one edge at a time until the sticker is completely lined up with the surface. Apply even pressure from the center of the sticker outwards to prevent air bubble formation.
Use a salt solution for temporary frosting. Dissolve salt in water and then paint or airbrush the solution onto the surface and allow to dry. The salt crystals in the solution will reform as it dries, leaving a frosted appearance on the clear surfaces. This "frost" can simply be washed away when desired.