1. Wash Radix Rubiae and Radix Rehmanniae, respectively, and put them in a casserole and soak them in cold water for one hour. The water quantity is less than1-2cm. Because the dosage is large, it is soaked in two pots respectively.
2. Cook madder first. When the fire boils, turn it down. After stewing for another hour, pour out the medicine juice. During this period, the residue was stirred for many times to make it heated evenly, and at the same time, it was also avoided that the residue was pasted to the bottom, which made the bottom of the pot heated unevenly and easily caused the pot to crack. After the medicine is boiled, the medicine juice should be filtered out immediately, otherwise the residue will absorb a lot of medicine juice.
3. Go back to the original place. When the fire boils, turn it down. After stewing for another hour, pour out the medicine juice. During this period, the residue was stirred several times to make it evenly heated. Sheng Di, avoid all metal appliances.
4. Mix the madder juice and the rehmannia juice together, put them in a casserole, and simmer with medium heat until bubbles appear in the medicine juice, and then continue to simmer for a while, and there will be more bubbles in the whole pot. Pour them into glass bottles while they are hot and collect them. This boiling process takes quite a long time, during which it needs to be stirred many times.