You’ll need three potatoes and three clean jars with lids.
Peel the potatoes and boil them for four or five minutes—just enough time to sterilize them, not cook them.
Remove one of the potatoes from the boiling water, using tongs. Place it immediately in a jar and put the lid on. Label this, “Boiled, Not Touched.”
Set the two other potatoes on a plate so they can cool. When they are cool enough to handle, have your child pick up the potato and handle it. Pass it back and forth between you. Then put this potato in a jar labeled “Boiled, Well-Handled.”
Now have everyone wash their hands thoroughly. Pick up the third potato. Do just what you did with the second, then put it in a jar labeled, “Boiled, Well-Handled, Clean Hands.”
Let all three containers sit in a shady spot for a week or so. Each day, have your child record what she sees in each jar. Don’t be surprised if she comes to the table with clean hands…without any reminding!