Shellac was coated onto highly permeable polymer films and its permeability calculated from measured values of permeance for coated and uncoated films. At 75per thousand relative humidity and 30°C, the O*l2*s and CO*l2*s permeability was 230 and 803 cc mil/(m*h2*s day atm), respectively, for Shellac coatings cast from ethanol. Over a wide range of relative humidities the water vapor permeability was 0.9-2.1 g mil/(m*h2*s day mmHg) for Shellac coatings cast from 2-propanol. Coatings made from water-soluble shellac were more permeable, especially at high values of relative humidity.