each cup.
worry, not all the salts will dissolve).
soak the string in water, and squeeze out the excess.
tie one washer to each end of the string, and put each end into one of the cups.
place the cardboard and cups somewhere where they will be left alone, such as on a shelf in your room, or on the counter in your kitchen (ask your parents' permission first!).
watch the middle of the string, just where it gets closest to the cardboard. you should see the water start to slowly drip from the string to the cardboard.
observe the cups and string every day at the same time for at least 7 days. each time 