Kids, all you really have to do in this "experiment" is chew your favorite kind of gum for a while. Think about what you learn here while you are chewing...

Bubble gum is a mixture of several chemicals, but rubber is the most important. A good bubble gum must be strong enough to stretch to a thin film without breaking, but still be soft enough to chew easily. That's a tall order. The other chemicals in bubble gum - resins, waxes, fillers, flavors, sugar, humectants, and emulsifiers - are all there either to provide flavor or to modify when and by how much the rubber stretches. Rubber molecules are polymers, which are long chain-like molecules formed when many smaller molecules bond together end to end. A natural polymer called latex, which is from trees, used to provide the stretchy part of bubble gum. Now many gum companies use a synthetic, food-grade version of the same rubber that goes into truck tires! This polymer is a mixture of styrene and butadiene and is abbreviated SBR.

Of the 20 or so chemicals in bubble gum, some dissolve in water and some do not. Most of the water-insoluble portion of bubble gum is called "gum base". That's where the rubber is. Some of the additives in the gum base actually restrict the size to which the bubbles can be blown on purpose, so as not to completely alienate parents! The most intense fragrances and flavorings in fruits are often essential oils like limonene (which is from orange and lemon rinds). They are well suited to gums because they are not water soluble and do not dissolve out of gum in your mouth. Gum does seem to lose flavor after a while, but that is usually because the sugar, which intensifies the fruit flavor, has dissolved.

Chemists must think of not only how the gum tastes and how big the bubbles get, but also how it feels in the mouth. It must soften without getting gooey, take up water without dissolving, and keep its flavor for as long as possible. On top of all that, it must not dry out on store shelves, should not stick to the wrapper, and be easy to work with in the factory. Chemists know how to tweak all the ingredients to make a formulation that is just right; who knew a simple thing like gum could be so complicated!

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Kathleen Carrado Gregar, PhD, Argonne National Labs 
[email protected]
February 1996

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Reference: Gail Marsella, ChemMatters, October 1994 (American Chemical Society, 1155 16th St., N.W.; Washington, DC 20036).