Frosting

The production of a fine crisp powder by methods other than simple grinding is known as frosting. The following methods exist:

1. One method is the defatting and grinding of seeds. The seeds are first sun-dried or stir-fried, the husks are removed, 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 stick together. Medicinals processed in this way include croton frost (Crotonis Semen Pulveratum, 巴豆霜 bā dòu shuāng) and trichosanthes seed frost (Trichosanthis Seminis Pulvis, 栝楼仁霜 guā lóu rén shuāng).
2. Another method, used to treat certain gourds, is efflorescence. For example, watermelon (Citrulli Fructus, 西瓜 xī guā) is frosted by gouging out a small lump to form a hole in which a small amount of mirabilite (Natrii Sulfas, 芒硝 máng xiāo) is placed. The lump is then replaced, and the watermelon is hung up to air. The mirabilite (Natrii Sulfas, 芒硝 máng xiāo) comes out and effloresces so that a fine, white frost forms on the surface of the watermelon, which when brushed off is ready to use.
3. The production of persimmon frost (Kaki Saccharum, 柿霜 shì shuāng) represents a third method of frosting: dried persimmon (Kaki Fructus Exsiccatus, 柿饼 shì bǐng) is exposed 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.