Taylor Made: Inner workings of the Etch a Sketch
First off, welcome to another semester!
Inspired by the ability of aluminum powder to stick to glass, French electrician André Cassagnes had an idea for a new toy. He produced L’Ecran Magique (The Magic Screen) in 1955, known today as the Etch a Sketch.
The outer surface of aluminum oxidizes easily, meaning it becomes ionic by losing electrons (think redox from chemistry). The product of the oxidation reaction, aluminum oxide, sticks to the original aluminum piece and protects the surface from further decay. In an Etch a Sketch, the charged powder is attracted to the glass.
The Etch a Sketch has a stylus mounted on a pair of orthogonal rods, one horizontal and the other vertical. The rods are each connected to a knob via steel wire. Their combined motion allows the stylus to move anywhere within its plane. The stylus scrapes powder away from the glass as it moves, creating a line.
The aluminum powder contains small beads that prevent it from clumping or sticking. Shaking the Etch a Sketch causes powder to recoat the surface of the glass, effectively erasing the drawing.
A common pastime of the Etch a Sketch is to create complex, albeit ephemeral, drawings and copies. For example, Chicago resident Jane Labowitch copied “A Sunday on La Grande Jatte” using an Etch a Sketch. Unlike most other media, the Etch a Sketch has a significant constraint- the stylus can’t be lifted off the glass, so everything drawn amounts to one continuous line. Additionally, mistakes can’t be isolated and need to either be used/masked or erased at the expense of the rest of the drawing. Labowitch’s copy took eight hours to complete.
The science behind an Etch a Sketch is similar to powder coating, in which charged particles of plastic powder are applied to a metal object of opposite charge. The attraction assures an even coating. The piece is then heated in an oven to melt the particles, completing the coating.