If you want to dye your hair with black beans for a long time, you need to match it with rice vinegar.

1. Put the black beans and rice vinegar into the pot, cook the black beans over high fire, and then remove the residue to get the juice. Then boil the decoction into a thick paste.

2. Every time you dye your hair, you can apply a proper amount of this medicine juice to your hair and wash your hair after half an hour.

3. Chinese medicine believes that black beans are sweet and flat, and have the effects of promoting blood circulation and diuresis, expelling wind and detoxifying, tonifying deficiency and nourishing blood, and benefiting kidney and blackening hair. Therefore, there is a basis for dyeing black beans. However, in the past, Chinese medicine used black beans to dye their hair. This method of external use of black beans provides a new idea for how to better play the role of black beans in blackening hair.

4. Rice vinegar can separate and concentrate melanin in black beans and attach it to hair. Therefore, this black bean rice vinegar does have the effect of dyeing hair, and it is harmless to human body.