Kids, in this activity you will learn how to make a thick - a very thick - liquid. It will be non-toxic, non-corrosive, cheap, and edible. It will, in fact, in many ways resemble a typical fast food restaurant milkshake.

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

You'll need 12 oz of water, and a tablespoon each of milk, chocolate syrup, and powdered xanthan gum. What in the world is xanthan gum and where do you find it? Most specialty health food stores and pharmacies should have some of this substance. When these ingredients are mixed in a blender for a few minutes, the result looks virtually indistinguishable from your local fast food shake. The taste won't be quite as good; however, you can add more syrup, or a touch of sugar or vanilla extract, and ice chips to make it closer.

What's happening here? Xanthan gum is a synthetic carbohydrate polymer, similar to natural gums. It is one of many common thickening agents used as food additives. It forms what is called a "hydrophillic colloid", or small particles that can soak up amazing amounts of water. Other examples are agar, arabic gum, bentonite (a clay!), celluloses, and polyethylene glycol. Look on lists of ingredients to find these substances, especially on "fat free" or "reduced fat" alternatives (they replace the smoothness of the fat). You may also find carrageenan, a polysaccharide derived from seaweed. Rumor has it that this is what is really used in those fast food shakes - so much for the actual amount of "milk" in them!

--------------

Kathleen Carrado Gregar, PhD, Argonne National Labs 
[email protected]
June 1997

----------------

Reference: Larry Lippman on the internet at: www.polymers.com/dotcom/pdcmag/
slime.html.