By Eric Brand and Nigel Wiseman

Frosting is a term used in Chinese herbal pharmacy. Basically, "frosting" (shuang) is the production of a fine crisp powder by methods other than simple grinding. Medicinals that are used in a "frost" form include Ba Dou, Bai Zi Ren, Xi Gua Shuang (watermelon frost), and Shi Shuang (persimmon frost). The following methods exist:

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One method is the defatting and grinding of seeds. The seeds are first sun-dried or stir-fried, the husks are re-moved, and the kernels are pounded to an almost paste-like consistency. The materials are sandwiched between layers of paper, and then sun-dried, baked, or pressed, so that the paper absorbs the oil. The paper is repeatedly changed until the materials are light, loose. and no longer sticking together. An example of a medicinal processed in this way is bā dòu shuāng (croton frost, Crotonis Seminis Pulvis). Bai Zi Ren (Biotae Semen) can also be processed this way to reduce its stool-freeing effect while preserving its spirit-quieting effect.

Another method, used to prepare certain gourds, is efflorescence. For example, xī guā (watermelon, Citrulli Fructus) is frosted by gouging out a small lump to form a hole in which a small amount of máng xiāo (Mirabilitum) is placed. The lump is then replaced, and the watermelon is hung up to air. The máng xiāo exudes and effloresces, so that a fine, white frost forms on the surface of the watermelon, which when brushed off is ready to use.

The production of shì shuāng (persimmon frost, Kaki Saccharum) represents a third method of frosting. Shì bǐng (dried persimmon, Kaki Fructus Exsiccatus) is ex-posed to the sun in the day and to the dew at night and then is covered to allow the skin to saccharify and form a frost.

Source: Concise Chinese Materia Medica (Brand & Wiseman), Paradigm Publications.