of Pennsylvania, sees it. “Historically, white is one of the ways men of the cloth signified their calling,” Brown says. Later, this association with religious purity evolved into bodily purity. (“Cleanliness is, indeed, next to godliness,” declared John Wesley in an 18th-century sermon.) Brown’s book, Foul Bodies, chronicles cleanliness in Europe beginning with its colonial expansion, and in early America up to the Civil War. Cleanliness, she says, was signified by a growing profusion of white undergarments, worn against the skin beneath the outer clothes, and then spilling forth in ruffled cuffs and collars. The undergarments were seen as having a cleansing power, the stains they collected a sign that they were drawing dirt from the body.

White became an indicator of class and wealth. The richer you were,to toothpastes to counteract yellow and give the illusion of clean white teeth. “Bluing” clothing with indigo in the wash is a centuries-old strategy to counteract yellow clothing stains in clothing.

Clearly, in the world according to copy paper, social status is marked by ascending levels of whiteness.

But bluing is an imperfect solution; the added color reduces the reflectance of the material, giving it a gray cast. Fluorescent compounds developed in the first half of the 20th century offered a perfect solution. In 1929, a German chemist named Paul Krais soaked fabric in an extract from horse chestnuts, which contained a fluorescent chemical, and noticed that the cloth became whiter and brighter. In the 1930s, chemists began developing similar compounds derived from ultraviolet light-responsive plant chemicals called stilbenes. One