Diaper Science

Have you ever changed a diaper and noticed those tiny crystals on the baby’s skin? Those tiny crystals are found inside the lining of the diaper and are made out of a non-toxic, moisture-absorbing polymer. Basically, it absorbs the baby’s pee so it doesn’t get all over the place.


  • Disposable diapers (several brands) – I suggest a cheap brand for a demonstration
  • Pure sodium polyacrylate powder (Optional. Can be found online or at a chemical supply store. Sometimes labeled as Insta-Sno or PolySnow)
  • Radish seeds (optional)
  • Ziploc bag
  • Scissors
  • 8-ounce plastic cup
  • Distilled water
  • Newspaper
  • Salt
  • Spoon
  1. Place a brand new diaper on a piece of newspaper. Carefully cut through the inside lining and remove all the cotton-like material. Put all this material into a clean Ziploc bag.
  2. Pick up any of powder that may have spilled onto the paper and put it into the bag with the stuffing. Blow a little air into the bag to make it puff up, then seal it.
  3. Shake the bag for a while to remove the powdery polymer from the cotton-like material. Notice how much, or how little, powder falls to the bottom of the bag.
  4. Carefully remove the stuffing and check out the dry powder you extracted.
  5. Pour this powder into a plastic cup and fill the cup with distilled water. Stir it around with your finger until the mixture begins to thicken.

What to do with your diaper gel:

  1. Try holding the cup upside down over a protected surface. Does the gel fall out?
  2. With the pure sodium polyacrylate powder you bought online or at a chemical supply store, you can perform a little magic trick! Put about a teaspoon of the powder in an OPAQUE cup ahead of time. Also add a little water to the powder so it won’t fall out. Next, get two other cups and place ALL the cups upside down. Now you’re ready for the trick. Gather your audience and make sure they see that all the cups are upside down. Then, turn them all right side up again. Pour about a half cup of water to the sodium polyacrylate and shift the cups around to try and “confuse” the audience. Now ask them which cup the water is in. Flip all the cups upside down and all the water will have “magically” disappeared!
  3. Submerge a fresh diaper in water for a minute or two. Take out the diaper and cut it open. What do you see?
  4. Try adding a couple teaspoons of salt to the diaper gel. What happens?
  5. Make some fresh diaper gel in a clear cup and add some radish seeds. Observe what happens over a period of several weeks.
  6. Store your diaper gel in a Ziploc bag.

How does it work?

The secret water-absorbing chemical in a diaper is a super-absorbent polymer called sodium polyacrylate. A polymer is simply a long chain of repeating molecules. If the prefix “poly” means many, then a polymer is a large molecule made up of many smaller units, called monomers, which are joined together. Some polymers are made up of millions of monomers.

Super-absorbent polymers expand tremendously when they come in contact with water because water is drawn into and held by the molecules of the polymer. They act like giant sponges. Some can soak up as much as 800 times their weight in water! That would be one wet baby!

The cotton-like fibers you removed from the diaper help to spread out both the polymer and the, uh, “water” so that baby doesn’t have to sit on a gooey lump of water-filled gel. It’s easy to see that even a little bit of powder will hold a huge quantity of water, but it does have its limits. At some point, baby will certainly let you know that the gel is full and it’s time for new undies!

In spite of their usefulness, these diapers can be a problem. If you’ve ever observed a baby in diapers splashing in a wading pool, you know that even one diaper can absorb lots and lots of water. Most public pools won’t allow them to be worn in the water because huge globs of gooey gel can leak out and make a mess of the filter system. Also, some folks used to throw them away in toilets – not a good idea unless you’re a plumber. For the most part, however, these diapers are a great invention and make for dry, happy babies.

Science Fair Connection:

A good science fair project changes something, creates a new experiment, and compares the results.

  • Change the brand of diaper and, using the steps listed above, test it to see just how much water it will absorb. Compare your results to the absorbency of the first diaper you tested.

The brand of diaper is the variable in this experiment. Be sure to use the same size of diaper even though you are using different brands. If you test a large Pampers diaper against a newborn-sized Huggies diaper, your results will not be reliable. Everything needs to stay the same except for the brand of diaper. You’ll find out extremely quickly if you get what you pay for or if there really isn’t a difference between the brands. Document your discoveries and share them at the science fair. Many moms with young children will thank you for your research!


Posted on April 23, 2013, in Uncategorized. Bookmark the permalink. Leave a comment.

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