Originally created with a crank instead of a push button, the salad spinner uses centrifugal force (similar to clothes dryers, meaning a motion away from a center point) to effectively drain the lettuce leaves so the dressing sticks and doesn’t get diluted, for example Illustrated Cook. The gadget we know today features a removable mesh bowl to easily separate and dispose of that unsightly water – a revelation how dirty that storehouse romaine head is.
So when you think about the mechanism behind this invention, the goal is really to just separate the lettuce from the water. In a spinner, the mesh bowl inside rids the lettuce of water and lets it drain into the larger bowl. Using this same concept, food writer Jill Santopietro (via Chowhound) suggested using a clean cotton pillowcase as a salad spinner substitute if you don’t have the kitchen gadget handy.
To do this, rinse the lettuce, then place it inside the pillowcase, squeeze it at the top and “spin it like a spinner.” Santopietro says you can also apply the same physics using a plastic bag lined with dry paper towels. Just add the lettuce inside, squeeze the plastic bag, and twist it around like you would the pillowcase. As with the salad spinner, when we spin the lettuce in a pillowcase, we rid the water of the lettuce by letting the cotton absorb this liquid, and the same goes for the paper towels in the bag in plastic. This helps clean the lettuce and dry it out faster.