ASTM C217/C217M-22 is a standard test method for evaluating the weathering resistance of slate. It is suitable for testing the resistance to efflorescences of slate in the natural environment. The standard evaluates the durability and Appearance Retention of slate by simulating its performance changes under conditions such as exposure to water, temperature changes, chemicals such as acid rain, etc. The test method includes steps such as soaking, drying cycles, and chemical reagent treatment, which aims to quantify the weathering resistance index of slate. The standard is suitable for quality control of slate for construction, especially in applications such as roofs, walls that require long-term weathering performance.