This standard provides a method for determining the application solubility and solution storage stability of water-soluble dyes within the temperature range of 40°C to 90°C. The method involves preparing and observing the state changes of a series of dye solutions with known concentrations at specified temperatures to determine their dissolution behavior under specific conditions. The core testing instruments include a Büchner funnel equipped with heating and suction filtration devices, as well as standardized filter paper, which are used to filter the solution at the test temperature to determine whether the dye is completely dissolved. This method is primarily used to evaluate the practical application performance of water-soluble dyes, rather than measuring their theoretical absolute solubility.