Blushing is a coating defect appearing as whitening on the coating surface when the application is performed at high relative humidity conditions. It is observed mostly when the coating is sprayed. The evaporation of the solvents from the coating during application leads to the decrease of film temperature to below the dew point of the humid air. 

Water condensation inside the film or on its surface results in resin and pigment precipitation or the formation of micro-cavities inside the film. The affected areas are observed as pale spots with low gloss. A recoating application that will be performed by removing the original coating layer from the surface is generally required to correct the surface appearance. Blushing can be prevented by reducing relative humidity and/or decreasing solvent evaporation rate. Rapid solvents with high “latent heat of evaporation” should be removed from the formulation. Blushing is critical especially for coatings that dry with evaporation (lacquers), however it may also be observed in oven coatings. Computer aided solvent mixture formulation is generally required to adjust the proper solvent balance, cost, viscosity and solvent mixture evaporation rate for coatings that dry by way of solvent evaporation.