Dahuang(Rhei Radix et Rhizoma), for example, cools the blood when used raw but when cooked, it becomes slightly warmer and has a blood-quickening effect. Heshouwu(Polygoni Multiflori Radix), when used raw, has a precipitating action, but after processing it loses this action and acquires the ability to supplement the liver and kidney.

Facilitating preparation and storage

Many vegetable products such as stems, leaves and roots must be properly sized before they can be used. These sized forms are called ”decocting pieces.” Similarly, minerals, shells and certain seeds must be crushed so they can be made into suitable prepared forms in which active ingredients are soluble. Some items need to be stir-fried or baked to remove water content to prevent them from rotting or becoming poisonous.

Removal of unwanted matter to increase purity, accuracy of measurement and ease of ingestion

For example, vegetable products are washed to remove soil. Pipaye(Eriobotryae Folium) is brushed to remove the hairs. Yuanzhi(Polygalae Radix) usually has its woody core removed. Haizao(Sargassum) is long-rinsed to remove its saltiness and fishy odor.

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