Viscosity

Fluidity degree of a coating that can be modified by adding solvents. It is very important for coating workability, according to the application method used: it is usually low for spraying, immersion or flow coating, medium for curtain coating and high for vertical spraying and roller coating. It is usually measured by DIN CUP viscometers. These viscometers are 100 cm³ cylindrical containers with a conic bottom provided with a 2, 4 or 8 mm hole. For example, if the diameter is 4 mm, the cup is called DIN no. 4. The cup is filled with coating and its discharge time expressed in seconds is the measure of viscosity. The discharge time (= viscosity) must be measured by a chronometer. Since viscosity is affected by test temperature, viscosity values in technical data sheets usually refer to a standard measurement temperature of 20°C.