How Does an Etch A Sketch Work?

We learned on February 2, 2013, that Etch A Sketch inventor André Cassagnes died last month in France. Here's a look back at his legendary toy.

In 1955, a French electrician named André Cassagnes got an idea for a new toy after seeing how an electrostatic charge could hold aluminum powder to glass. He worked up a prototype for the toy—based on the design of a television screen—in his basement workshop and called it “L'Ecran Magique,” or “the magic screen.” Its joystick, glass and aluminum powder allowed users to draw and erase images and letters with no ink and no mess. Cassagnes sought a patent, put couldn’t pull the money together to get one, so he borrowed from an investor, who sent an employee to pay the fee at the patent office. (The assistant’s name ended up on the patent, and he has often been wrongly credited with the invention of the toy in the decades since.)

Cassagnes’ investor, Paul Chaze, took the toy to several European toy fairs, but it drew little interest. Executives from the Ohio Art Company saw it at the 1959 International Toy Fair in Nuremburg, Germany, and didn’t think much of it at first, either. But they decided to take a chance on the product. [Image credit: The Invisible Agent]

Ohio Art paid $25,000 for the rights to the toy and had their chief engineer, Jerry Burger, collaborate with Cassagnes to perfect it. The company launched the toy in the United States under the name “Etch A Sketch” the following year, just in time for the holiday shopping season.

The Magic Beneath the Screen

When Ohio Art Co. executive William Casley Killgallon brought the toy back from Germany, his 21-year-old son Bill was mesmerized by it. “I was just fascinated,” he told the Toledo Blade in 2010. “I thought, 'How the heck is this working?' I was turning the knobs and just couldn't figure it out.”

And that’s part of the fun, isn’t it? Not knowing how it works? The idea – in a young, fertile imagination – that it might actually be magic? If you prefer to think of it that way, I can’t blame you, but you should stop reading, because here’s what’s going on under the screen:

When you turn the Etch A Sketch upside down and shake it, the inside surface of the screen gets coated with aluminum powder, which will stick to almost anything (mixed in with the powder are small polystyrene beads, which help it flow evenly and keep it from caking).

Also inside are horizontal and vertical bars connected by thin steel wires to the knobs on the face of the toy. A stylus is mounted where the two bars cross, so when you turn a knob, it moves its bar and the bar moves the stylus. As the stylus moves across the inside surface of the screen, it scrapes off the aluminum powder and creates a dark line on the light gray screen, which is just the darkness of the toy’s interior set against the lighter aluminum powder.

To erase their picture, an artist only needs to flip the toy and shake, redistributing the powder over the screen.

Etch A Sketch of Mass Destruction?

In the first season finale of the AMC series Breaking Bad, the protagonist Walter White makes some thermite using the aluminum powder from inside several Etch A Sketches and uses it to melt the lock off of a door he needs to get open. Would that actually work outside of an Emmy-winning TV series?

I’m no Jamie Hyneman, and my girlfriend won’t let me play with explosives in the house (this is, I suppose, her only flaw), so I can’t test this out myself, but it seems pretty straightforward and plausible.

Thermite is made from a metal powder and a metal oxide and produces an exothermic oxidation-reduction reaction, known as a thermite reaction, when heat is applied. This reaction creates extremely high temperatures around a small area and is used for welding in situations where there isn’t enough space for conventional welding equipment (some MIT students also once used it to weld a trolley to its tracks as a prank).

Fuels commonly used in thermite include powdered aluminum, magnesium, calcium and boron. Common oxidizers are boron(III) oxide, silicon(IV) oxide, manganese(IV) oxide and  iron(III) oxide.

Empty a few Etch a Sketchs and you’ve got a small amount of aluminum powder, so all Walter would need is a metal oxide. Iron(III) oxide is easy enough to get (it’s used as a pigment and as “jeweler's rouge”), and an aluminum-iron(III) oxide thermite would easily reach 4500+ degrees (Fahrenheit), enough to melt a steel padlock.

Big Questions
Where Did the Myth That Radiation Glows Green Come From?

by C Stuart Hardwick

Probably from radium, which was widely used in self-luminous paint starting in 1908. When mixed with phosphorescent copper-doped zinc sulfide, radium emits a characteristic green glow:


The use of radioluminescent paint was mostly phased out by the mid-1960s. Today, in applications where it is warranted (like spacecraft instrument dials and certain types of sensors, for example), the radiation source is tritium (radioactive hydrogen) or an isotope of promethium, either of which has a vastly shorter half life than radium.

In most consumer products, though, radioluminescence has been replaced by photoluminescence, phosphors that emit light of one frequency after absorbing photons of a difference frequency. Glow-in-the-dark items that recharge to full brightness after brief exposure to sunlight or a fluorescent light only to dim again over a couple of hours are photoluminescent, and contain no radiation.

An aside on aging radium: By now, most radium paint manufactured early in the 20th century has lost most of its glow, but it’s still radioactive. The isotope of radium used has a half life of 1200 years, but the chemical phosphor that makes it glow has broken down from the constant radiation—so if you have luminescent antiques that barely glow, you might want to have them tested with a Geiger counter and take appropriate precautions. The radiation emitted is completely harmless as long as you don’t ingest or inhale the radium—in which case it becomes a serious cancer risk. So as the tell-tale glow continues to fade, how will you prevent your ancient watch dial or whatever from deteriorating and contaminating your great, great grandchildren’s home, or ending up in a landfill and in the local water supply?

Even without the phosphor, pure radium emits enough alpha particles to excite nitrogen in the air, causing it to glow. The color isn’t green, through, but a pale blue similar to that of an electric arc.


This glow (though not the color) entered the public consciousness through this early illustration of its appearance in Marie Curie’s lab, and became confused with the green glow of radium paints.

The myth is likely kept alive by the phenomenon of Cherenkov glow, which arises when a charged particle (such as an electron or proton) from submerged sources exceeds the local speed of light through the surrounding water.

So in reality, some radionuclides do glow (notably radium and actinium), but not as brightly or in the color people think. Plutonium doesn’t, no matter what Homer Simpson thinks, unless it’s Pu-238—which has such a short half life, it heats itself red hot.


This post originally appeared on Quora. Click here to view.

Jack Taylor, Getty Images
Big Questions
How Are Royal Babies Named?
Jack Taylor, Getty Images
Jack Taylor, Getty Images

After much anticipation, England's royal family has finally received a tiny new addition. The birth of the Duke and Duchess of Cambridge's second son was confirmed by Kensington Palace on April 23, but the name of the royal newborn has yet to be announced. For the heir to the British throne and his wife, choosing a name for their third child—who is already fifth in line to the throne—likely won't be as easy as flipping through a baby name book; it's tradition for royals to select names that honor important figures from British history.

According to ABC WJLA, selecting three or four names is typical when naming a royal baby. Will and Kate followed this unwritten rule when naming their first child, George Alexander Louis, and their second, Charlotte Elizabeth Diana. Each name is an opportunity to pay homage to a different British royal who came before them. Some royal monikers have less savory connotations (Prince Harry's given name, Henry, is reminiscent of a certain wife-beheading monarch), but typically royal babies are named for people who held a significant and honorable spot in the family tree.

Because there's a limited pool of honorable monarchs from which to choose, placing bets on the royal baby name as the due date approaches has become a popular British pastime. One name that keeps cropping up this time around is James; the original King James ruled in the early 17th century, and it has been 330 years since a monarch named James wore the crown.

If the royal family does go with James for the first name of their youngest son, that still leaves at least a couple of slots to be filled. So far, the couple has stuck with three names each for their children, but there doesn't seem to be a limit; Edward VIII, who abdicated the throne to George VI in 1936, shouldered the full name of Edward Albert Christian George Andrew Patrick David.

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