Once, when readers wanted to remember something, they had to mark important passages with thin, wobbly lines in drab, hard-to-relocate colors. Before the rise of the highlighter, says Dennis Baron, a University of Illinois professor and the author of “A Better Pencil,” attentive readers relied on “a combination of underlining and marginal notes.”
Like so much else, that began to change in the 1960s. It was then that the Japanese inventor Yukio Horie created a felt-tip pen that used water-based ink. The following year, in 1963, the Massachusetts print-media giant Carter’s Ink developed a similar water-based marker that emitted an eye-catching translucent ink. They called it the Hi-Liter.
As with Horie’s invention, capillary action pulled ink through a filter — similar to the one in a cigarette — to the paper’s surface when a writer pressed the highlighter to paper. Just as important as the ink’s smooth, even application was its color: see-through yellow and pink, which both drew the eye and neatly delineated a piece of text without obscuring it. The fact that the highlighter’s ink was water-based, rather than alcohol-based, helped prevent it from seeping through paper.