Kids, a while back we learned how to make slime in this column. Now it is time to make GACK, a similar material that is made from easy-to-find ingredients.  

Please note:  All chemicals and experiments can entail an element of risk, and no experiments should be performed without proper adult supervision.

 In one container mix 4 oz. Elmer's glue (water-soluble) with 4 oz. water, and set it aside. In another container, mix 1/2 cup of water with one teaspoon borax (which is sodium borate) and stir. Mix the two solutions and add a few drops of food coloring for effect. Mix very well until you have a solid mass.

Both Gack and Slime are examples of what are called non-Newtonian fluids. Your gack can be kneaded into an elastic, semi-rigid glob that has dramatic physical properties. If the gack is simply suspended from your hand, it will flow and stretch. It can also be stretched by slowly pulling, but it will break if pulled quickly. When placed in a container the gack assumes the shape of the container. Similarly, it will flow into a film on a flat surface.

This recipe can be easily scaled up to make large quantities of gack. If you want to have enough for all your classmates, for example, two-liter pop bottles can be used to make the two solutions ahead of time. Then use a dishpan to mix the ingredients. It is easiest to simply use your hands to mix up the gack; if you choose this method wear playtex gloves.

(Safety Tip: Do not eat any of your experiments).

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Kathleen Carrado Gregar, PhD, Argonne National Labs 
[email protected]
December 1994