This standard provides a classic method for determining the density of liquid resins. Its core principle involves using a precisely calibrated pycnometer to measure the mass difference between equal volumes of the sample and a liquid of known density (such as water), thereby calculating the density. This method is primarily applicable to liquid resins with low to medium viscosity. Typical instruments required for the test include a calibrated pycnometer, an analytical balance with an accuracy of at least 0.1 mg, a constant-temperature water bath for maintaining stable temperatures, and a vacuum desiccator for degassing. As a fundamental physical property test, this method holds practical significance for material development, quality control, and trade.