A Detailed Explanation of the Water Grinding Method: The Traditional Technique for Turning Mineral Medicinal Materials into Fine Powder

Water grinding is a traditional processing method in the preparation of Chinese medicinal materials and belongs to the category of water processing methods. It involves adding water to mineral or shell-based drugs that are hard in texture and insoluble in water and grinding them together, then using the difference in the ability of coarse and fine powders to remain suspended in water to collect the upper suspension, let it settle, and dry it, ultimately obtaining an extremely fine medicinal powder.

During operation, first crush the medicinal material, place it in a mortar or grinding container, add an appropriate amount of clean water, and grind it into a paste, then add a larger amount of water and stir. The coarser particles will naturally sink, while the fine powder remains suspended in the water. At this point, pour off the upper suspension and let it stand to settle, discard the clear water, and take out the sediment to dry. After repeating this several times, the powder can reach the desired fineness.

The significance of water grinding is mainly reflected in three aspects. First, it makes the medicinal powder fine enough to facilitate the preparation of pills and powders or direct external application; second, during grinding and decanting, it removes some water-soluble impurities or toxic components; third, it avoids loss caused by dust flying during dry grinding. Medicinal materials with hard textures such as cinnabar, calamine, talc, and pearl are often treated by this method.

It should be noted that not all medicinal materials are suitable for water grinding. Drugs that dissolve easily in water, deteriorate easily, or whose active ingredients would be lost with the water are generally not treated by this method. In modern Chinese medicine production, many steps have been replaced by mechanical crushing such as ball mills, but the principle of water grinding is still used. In traditional preparations and manual processing, it remains a classic means of ensuring that medicinal powder is fine and uniform.