Method: You can wash the walnut black stains on your hands with lemon juice. Lemon contains a lot of citric acid, and raw walnut skin contains alkaloids. Acidic substances in lemon and alkaline substances in walnut skin can be neutralized to remove dirt from walnut skin.

Material preparation: 1 lemon, kitchen knife, paper towel.

The specific operation steps are as follows:

1. First, cut the lemon in half with a knife, as shown in the figure below.

2. Then squeeze the lemon by hand, let the lemon juice drop to the position where the hand turns black after peeling the raw walnut, and then knead it.

3. Next, wash the dirt off your hands with cold water.

4. Then wipe off the water stains on your hands with paper towels.