The substrate is held by vacuum on a chuck. The material to be deposited is dissolved in a solvent. The solution is applied to the substrate, which is then rotated at high speed. The rotation spreads the solution evenly over the surface and also causes some of the solvent to evaporate leaving a thin film of material on the substrate. The substrate is usually baked immediately after spin casting to remove the remaining solvent in the film. The process is typically performed on one side of the substrate at a time.