One pound of black beans and two pounds of vinegar plus 100 ml of water.

Specific method:

1. Prepare 500 grams of black beans and 1000 ml of vinegar.

2. Pour the black beans and vinegar into the water, stir evenly, simmer over low heat for more than 40 minutes, and concentrate into a paste. After 15 minutes of storage, the beans can be filtered out with gauze.

3. After cooling, use a brush to apply the black bean paste evenly on the hair, especially the white hair areas, and comb the hair repeatedly for 10 to 15 minutes.

4. Leave it on for more than 30 minutes before coloring, and then rinse it clean.