In the name of science and Silly Putty, here we are puttering around with the stuff in our lunchroom.

Image courtesy Elizabeth Johnston/HowStuffWorks.com

Homemade Silly Putty

Teachers love Silly Putty because it embodies the spirit of hands-on science -- and because it offers a fun way to demonstrate how polymers, or long chains of molecules repeated over and over again, work. But buying putty-filled eggs for an entire classroom can be cost-prohibitive. Luckily, it's not too hard to whip up a little private label Silly Putty using ingredients you can find around the house or at the drugstore. The most common recipe uses the following:

  • white craft glue (Elmer's brand works well)
  • borax (20 Mule Team Borax is a common brand)
  • water
  • food coloring (if you want colored putty)

No chemistry experiment is complete without some equipment. You'll need measuring spoons and a measuring cup to get the right proportions for the mixture. You'll also need a large bowl, a small plastic cup and a spoon to mix ingredients together. You might also have a resealable plastic bag or container on hand if you want to save your homemade putty for a few days.

Once you have all of your supplies, you're ready to get silly. Just follow these steps, and you'll be playing with putty in no time:

  1. Empty an 8-ounce (237-milliliter) bottle of glue into the large bowl.
  2. Fill the glue bottle with warm water, shake and pour what remains in the bowl.
  3. Give everything a gentle stir.
  4. Optional: Add a drop or two of food coloring to the glue-water mixture and stir some more. If you don't add food coloring, your finished putty will be white.
  5. In the small plastic cup, add a teaspoon (5 milliliters) of borax powder to 0.5 cup (4 ounces or 118 milliliters) of warm water. Stir the solution.
  6. While stirring the glue-water mixture, slowly add a little bit of the borax solution. You should feel the viscosity increase immediately. Keep adding small amounts of borax solution as you stir until you get a consistency like soft, but firm, window putty. At some point, you should start using your hands to mix and knead the material.
  7. Store in a resealable bag or container to keep soft.

This concoction will undoubtedly impress your friends, but they'll be even more impressed if they hear you explain the chemistry. Here's what's happening: Glue contains a polymer called polyvinyl alcohol, or PVA. In the glue-water mixture, these polymer chains slip and slide past each other easily. But when you add the borax solution to the glue, it connects one PVA molecule to another in a process known as cross-linking. As more chains link up, they no longer slip and slide. Instead, they form a large mat that resembles a net or a spider's web. This is what gives the material its puttylike qualities.

Of course, nothing beats the original Silly Putty you can buy at the toy store. Snap up more links to classic toy tidbits next.