Science in Your Cereal Bowl!

Fun & Games Science
cap'n crunch
Cap’n Crunch’s whistle, with its 2,600Hz squeal, became a favorite tool for phone system hackers.

Cereal manufacturers learned early on that an inexpensive giveaway inside a box of cereal could inspire a purchase and create brand loyalty with moms and kids. From the 1950s on, the cereal aisle in the grocery store became a mini toy shop with an end-less array of plastic baubles, punch-out character masks, and collectible trinkets. Amid the secret decoder rings and cowboy sheriff badges were some cleverly designed toys that ingeniously used scientific principles to amaze and entertain.

Here’s a look at six classic cereal premiums that built inquisitive young minds.

1. Bo’sun Whistle

How did a simple cereal-prize whistle empower an early phone-phreaking hacker and inspire the founders of Apple Computer? Starting in the mid-1960s, Quaker Oats packed free Bo’sun Whistles inside boxes of Cap’n Crunch cereal. This plastic giveaway produced a piercing two-toned blast that (like a real bosun’s whistle) could be heard over the sounds of the sea or in bad weather.

Coincidentally, the whistle’s perfectly pitched 2,600Hz tone could also be heard by AT&T’s analog telephone trunk line-switching circuits. Tricking the billing circuits resulted in free (well, stolen) long distance phone calls. Phone phreaker and computer programmer John Draper, nicknamed “Captain Crunch” for infamously demonstrating this slick whistle trick, went on to develop electronic tone-generating circuits to do the same thing.

Draper’s technical skills impressed a young Steve Wozniak, who hired him to create circuits for Apple Computer. Unfortunately, publicity from a magazine article “blew the whistle” on Draper, and he was convicted on toll fraud charges. He wrote the first word processing software for the Apple II while in “the brig.” Today’s digital phone circuits are unaffected by these nautical noisemakers.

frosted flakes
How do you control Diving Tony? Only you (and millions of other kids of the 1980s) know the secret.

2. Diving Tony

Kellogg’s Frosted Flakes featured Diving Tony, a witty 1980s remake of a classic scientific toy, the Cartesian diver (named for the 17th-century French philosopher René Descartes). This miniature version of Tony the Tiger mysteriously obeyed your commands, diving and rising inside a water-filled plastic soda bottle. Gr-r-reat! — but how did it work?

The scientific secret used the incompressibility of water along with the ideal gas law: the volume of a gas is inversely proportionate to the pressure on it. The plastic Tony was molded to be neutrally buoyant and float near the top of the bottle. When you squeezed the bottle, the pressure on the water compressed the air bubble inside Tony. The reduced bubble displaced less water, making Tony less buoyant, and he sunk to the bottom.

When you released the pressure, the bubble expanded and displaced more water, so Tony became buoyant again and rose back up. Because you couldn’t see the bottle being squeezed, the up and down diving action seemed magical!

3. Balloon-Powered Toys

There were many balloon-powered cereal toys, but they all obeyed Newton’s third law, about the mutual forces of action and reaction between two bodies. The force created by a jet of air escaping from a rubber balloon was powerful enough to propel a toy car in the opposite direction.

As early as 1950, Kellogg’s offered a Jet-Drive Whistle Loco, available by mail for 25 cents and a box top from Kellogg’s Corn Flakes. According to the promotional literature at the time, the 4″-long injection-molded plastic steam locomotive was “accurately scaled — even the rivets show.” The corny sales pitch to grocers touted: “All steamed up and ready to go! Get aboard — here’s your ticket to biggest sales yet. Is there a kid in America who wouldn’t want one?” Only the mailman knew for sure.

This science-based gimmick is an irresistible force that kept coming back. In 1961, Nabisco’s Rice and Wheat Honeys cereals came with updated Racing Robot and Speeding Spaceman variations. By the 1970s, Quaker Oats included its own version: Balloon Racers, free inside boxes of Cap’n Crunch-brand cereals.

The more compact 2½” design kept plastic costs down and — thanks to Newton’s second law, force = mass × acceleration — kept car speeds up. With less mass, these smaller cars featuring the Cap’n, Jean LaFoote, and Smedley (the Peanut Butter Crunch elephant) went even faster on the same balloon power.

4. Optical Toys

The science of optics has also proved to be a popular platform for premiums. Periscopes, spyglasses, and lenticular lens “wiggle pictures” have all been offered as fun freebies. You almost need a real magnifying glass just to see the Wheaties Microscope, a real working mini-microscope, offered free in cereal boxes starting in the 1950s. More of a miniature magnifying glass, the single plastic lens in an adjustable eyepiece tube afforded very limited magnification and plenty of optical distortion — but it really worked!

5. Kinetic Energy Toys

The science behind even the simplest toy top or yo-yo could make your head spin. The kinetic energy of a flywheel is described by the formula Ek = ½ Iω2, where E is the amount of kinetic energy, ω is the angular velocity (how fast it’s spinning), and I is the moment of inertia (resistance to change in spin). To find the moment of inertia for a disk with a large center hole, just use I = ½ m(r12 + r22). Got that?

Fortunately no math skills were required to have fun with the Gyro-Cycle or Flywheel Car premiums in Quisp cereal from Quaker Oats, which originally landed on shelves in 1965. One tug of the rack-and-pinion geared pull strip and the mini-flywheel instantly revved up to high speed (plenty of ω!). The clever design also included a metal disk in the flywheel (much more mass than a plastic one) for increased I. All that ω and I resulted in enough kinetic energy to send Quisp, the spin-powered spaceman, quickly zipping across the floor.

6. Baking Powder Power!

One classic cereal toy has stayed crunchy in the milk of time for over 50 years: the baking powder-powered diving sub. In 1955, boxes of Kellogg’s Rice Krispies promised “FREE INSIDE! An actual working ATOM SUB!” In reality, a simple kitchen chemical reaction provided the fuel for millions of these miniature marvels. A pinch of baking powder from mom’s pantry contained both an alkaline, sodium bicarbonate (NaHCO3); and an acid, cream of tartar (potassium bitartrate, KC4H5O6). When combined in water, the two react: NaHCO3 + KHC4H4O6 → KNaC4H4O6 + H2O + CO2 producing a salt, water, and carbon dioxide gas, CO2. In recipes, the CO2 makes quick breads and muffins rise. In this case, the CO2 makes toy submarines rise. The buoyant force of the bubbles formed is enough to lift the submerged sub. When it surfaces, the sub tips to one side, the bubbles are released, the sub sinks, and the cycle repeats.

Over the years, there have been many versions of this buoyant bubbling toy: submarines, diving frogmen in assorted sizes, killer whales, sharks, and mechanical monsters. And though the most famous was the 1955 submarine design, a patent search finds a design dating from 1920. Who knows how many other versions are floating around?

Make it!

spud sub

Hey kids! Now you can make your own version of the famous diving sub! No box tops needed — just flip to page 164 of MAKE Volume 26. “Toy Inventor’s Notebook” shows how to make your own working version of the diving sub from a potato: a Diving SpudMarine!

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Bob Knetzger

Bob Knetzger ( is an inventor/designer with 30 years of experience making fun stuff.

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