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.