Restroom Illusions

There's something to tickle the eye just about anywhere you go at San Francisco's Exploratorium—even the restrooms.

The entryway to the main pair of restrooms features a dramatic array of black and white ceramic tiles, carefully arranged to recreate an optical effect known as the Café Wall Illusion. Described and popularized by psychologist Richard Gregory, the illusion makes the parallel lines defining each row of tiles appear sloped at different angles to each other.

The tiles, alternating black and white, are in parallel rows, but because the rows are staggered, the dividing lines between the rows look slanted.

The effect is most dramatic when the grout between the tiles is an intermediate gray in color, rather than either black or white. In the Exploratorium installation, each of three walls features grout of a different color (gray in the middle, white on the men's side, and black on the women's side) so that viewers can judge the effect of grout color on the strength of the illusion.

The eye-dazzling show doesn't end there. Within the restrooms throughout the building, individual tiles feature other classic optical illusions—all shown in black against white.

The patterned tiles were custom manufactured, then scattered among the white tiles covering the walls.

That's quite a show for a simple rest stop.

Photos by I. Peterson