White

White is a colour (or, as some call it, the absence of colour) that results when light reaching the eye contains all wavelengths of visible light in equal proportion. A white object reflects a large portion of the light that falls on it, without absorbing particular wavelengths. For this reason, white, black, and grey are classified as colours without hue—their distinction depends only on the amount of light reflected.

In colour systems used in art and technology, white occupies a specific position. In the RGB system—in which light is mixed together, as on screens—white is obtained when red, green, and blue are all at maximum intensity. In the CMYK system used in printing, where colours are subtracted from light, white is where no colour is applied: it is the colour of the paper or base surface.

How white is produced

Materials used to create white include titanium dioxide, zinc oxide, and calcium carbonate. These substances have a high capacity to reflect light. Titanium dioxide is now the most widely used white pigment in the world, employed in paint, paper, plastic, and even food and medicine. Historically, lead white (a pigment made from lead) was used, but its use declined after the toxicity of lead was established.

The nature of white

Snow, foam, and clouds appear white not because white matter is present, but because they consist of many tiny particles or crystals that scatter light in different directions. Similarly, water and ice with large crystals appear clear or blue-tinted. Snow reflects much light, which is part of how the Earth regulates its temperature (albedo).

Social and cultural meaning

Many societies associate white with cleanliness, peace, and purity. A white flag is recognized as a symbol of ceasefire or surrender. In Islam, white cloth worn during ihram (the state of ritual consecration) is put on for pilgrimage and umrah, and the dead are shrouded in white. Some cultures associate white with weddings; others associate it with funerals. The meaning of a colour depends on culture, not on any property of the colour itself.