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The Silly Putty or slime experiment – how to make green slime at home.

Pouring Oobleck Slime out of its bucket

Fine times with homemade slime (or silly putty if we tweak it up a bit)

Man and girl covered in slime on the Nickelodeon game show

At some point, you may have heard someone having a casual conversation in the checkout line speak of “polymers.” A polymer is a large molecule that is made of repeating structural units. These units are connected by what is called a covalent chemical bond. A well-known polymer is “plastic.”

In this experiment, we will make a polymer and then add a substance that will cause the polymer chains to cross link. Cross-links are bonds that link one polymer chain to another. When the polymer chains are more “bound together,” they become harder to move around and begin to gel. It’s an odd type of polymer because it has the qualities of both a solid and a liquid.

  1. In a bowl, mix an equal quantity of Elmer’s glue and water.
  2. Fill a jar with a cup of water and mix in a tablespoon of borax. Borax is a form of soap. We will continue mixing in borax until the solution is saturated.
  3. Put the lid on the jar and shake well keeping an eye on how well the borax powder dissolves.
  4. If the borax powder dissolves, add more borax. When you get to a point where no more borax will dissolve, then the solution is “saturated”.
  5. Add about two tablespoons of the borax solution to the bowl of Elmer’s glue and water mixture. Stir quickly.
  6. If you’d like, add brown food coloring if you’re trying to make silly putty or green food dye if you’re trying to make slime.

The science behind the slime solution

Kids playing with slime in a huge vat

You may have to experiment a few times to determine how much borax solution to add. If you don’t add enough borax the slime will contain too much glue, which is the polymer part, and will be too sticky. Simply add more borax. Too much borax and you’ll have too much “cross linking”, and the stuff will be too wet. Take it out and kneed it with your hands – the extra borax solution will evaporate.

The Elmer’s glue and water mixture, the polymer, is known as polyvinyl acetate. The borax solution, the cross-linking agent, is known as sodium tetraborate. Again, experiment with the amount of borax solution to see what is needed to make the slime thicker (aka silly putty) or thinner (aka slime).

Note: another name for this substance is Gak which is sold as a trade name polymer known as poly-vinyl alcohol.

What to do with this newfound stuff?

Suggested uses for your new substances? Take a dab of green slime and wipe under your nose. Then tell Mom you’re not feeling well. Or take the brown silly putty and place a lump on Dad’s chair right before he sits down. When he stands up make a scrunched-up face and say “Ewwww, you’re gross”.

Advance notes about the homemade slime experiment

Purple slime

In the United States it is known as “slime” but in the British Isles, they call it “Gunge”. 

The slime you see on TV (it’s been used in television shows since the 1960’s) is made with an industrial thickener called Natrosol (strangely enough, Natrosol is primarily used in the making of sauce for apple pies).

Have your students extend the experiment by answering these questions:

How can you make the polymer stretch the farthest? Does the amount of Borax added change the slime? What method of storage will make the polymer last the longest? What brand of glue makes the stretchiest polymer? Does the amount of water added to the glue affect the gooeyness of the slime?

Experiment Supplies

Supplies: Food dye, Glass jar, Glue, Borax

Image Credits

In-Article Image Credits

Purple slime via Wikimedia Commons with usage type - GNU Free. August 18, 2007
Man and girl covered in slime on the Nickelodeon game show via Wikimedia Commons by Nick Hotel with usage type - Creative Commons License. 2008. Modified to crop logo.
Kids playing with slime in a huge vat via Wikimedia Commons by Okras with usage type - Creative Commons License. August 31, 2019

Featured Image Credit

Pouring Oobleck Slime out of its bucket via Wikimedia Commons by Ciphers with usage type - Creative Commons License. July 12, 2009


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