This standard specifies a method for measuring the outflow time of paints, varnishes, and related products to monitor their viscosity. The core principle involves using a standardized outflow cup to measure the time required for a specified volume of liquid to flow through a small orifice at the bottom under gravity. The outflow time directly reflects the viscosity of the liquid. The standard details four types of outflow cups with orifice diameters of 3 mm, 4 mm, 5 mm, and 6 mm, and provides methods for their calibration. During testing, in addition to the outflow cup, timing devices such as stopwatches are typically used, and measurements are conducted under constant temperature conditions (e.g., 25 ± 0.5°C) to ensure accuracy and repeatability of results. This method is applicable to materials for which the liquid flow endpoint can be accurately determined. However, for materials with excessively long outflow times (close to 100 seconds), the accuracy of the measurement may decrease.