Lemon juice
Milk
Baking soda solution
White vinegar
Sugar water
Onion juice
Heat source for revealing the writing
Cotton swab, paintbrush, or toothpick for applying the ink
Lemon juice
Milk
Baking soda solution
White vinegar
Sugar water
Onion juice
Heat source for revealing the writing
Cotton swab, paintbrush, or toothpick for applying the ink