By vibrating or oscillating a screen, particles smaller than a given aperture pass through this being thus separated from the remaining mixture. Industrial screening is normally operated at high capacities, so that efficiency is expected to be lower when compared with laboratory screening, which is operated at a lower scale. Efficiencies between 85% and 95% are considered reasonable for both scales of screening. A description of the unit operations immediately preceding and following is quite relevant. Details of the equipment adjacent to the screening step must be carefully considered. The screening operation involved should also describe the methods used for controlling feed rate, product collection, required screen efficiency, number and size of products, and so on. Predrying of materials using heated screen cloths, or going wet by adding water sprays, are all equally effective in damp screening. Industrial screening equipment is used over a wide range of particle sizes.