Application viscosity describes the resistance of a paint or varnish to flow during processing. In practice, it is measured using flow cups (e.g. DIN 4 mm) in seconds. Viscosity that is too high makes application difficult and leaves brush or roller marks, while viscosity that is too low leads to runs and sags. Temperature, solvent or water content, and pigment load all affect viscosity. Spray application requires specific processing viscosities depending on the equipment used. By carefully thinning with the recommended diluent, application viscosity can be adapted to the chosen application tool and ambient temperature conditions.