All you need is a lemon, bowl to squeeze the lemon juice in, white paper, q-tips, and a heat gun (or something else that produces heat).
Let your kids squeeze the lemon juice into the bowl. Make sure to let your kids lick the lemon to see what it tastes like. Have the camera ready for some funny faces. Give each child a q-tip, dip it in the lemon juice and paint on the paper. When they are finished, let the paper dry completely. Once they are dry, use your heat gun to reveal their pictures.
These are the dried pictures before using the heat gun.
Their images are revealed!