Optics Brown is a dark orange color. It can be thought of as dark
orange, but it can also be made in other ways. In the
RGB color model, which uses red, green and blue light in various combinations to make all the colors on computer and television screens, it is made by mixing red and green light. In terms of the
visible spectrum, "brown" refers to long wavelength hues,
yellow,
orange, or
red, in combination with low
luminance or
saturation. Since
brown may cover a wide range of the visible spectrum, composite adjectives are used such as red brown, yellowish brown, dark brown or light brown. As a color of low intensity, brown is a
tertiary color: a mix of the three subtractive
primary colors is brown if the
cyan content is low. Brown exists as a color perception only in the presence of a brighter color contrast. Yellow, orange, red, or rose objects are still perceived as such if the general illumination level is low, despite reflecting the same amount of red or orange light as a brown object would in normal lighting conditions. File:Optical grey squares orange brown.svg|The colored disks appear to be brown and orange, but are actually an identical shade; their perceived color depends on the shade of grey they are surrounded by
Brown pigments, dyes and inks • Raw
umber and burnt umber are two of the oldest pigments used by humans. Umber is a brown clay, containing a large amount of
iron oxide and between five and twenty percent
manganese oxide, which give the color. Its shade varies from a greenish brown to a dark brown. It takes its name from the Italian region of
Umbria, where it was formerly mined. The principal source today is the island of
Cyprus. Burnt umber is the same pigment which has been roasted (calcined), which turns the pigment darker and more reddish. • Raw
sienna and burnt sienna are also clay pigments rich in iron oxide, which were mined during the
Renaissance around the city of Siena in Tuscany. Sienna contains less than five percent manganese. The natural sienna earth is a dark yellow
ochre color; when roasted it becomes a rich reddish brown called burnt sienna. •
Caput mortuum is a haematite iron oxide pigment, used in painting. The name is also used in reference to mummy brown. •
Van Dyck brown, known in Europe as Cologne earth or Cassel earth, is another natural earth pigment, that was made up largely of decayed vegetal matter. It made a rich dark brown, and was widely used during the Renaissance to the 19th century It takes its name from the painter
Anthony van Dyck, but it was used by many other artists before him. It was highly unstable and unreliable, so its use was abandoned by the 20th century, though the name continues to be used for modern synthetic pigments. The color of Van Dyck brown can be recreated by mixing ivory black with mauve or with Venetian red, or mixing cadmium red with cobalt blue. •
Mars brown. The names of the earth colors are still used, but very few modern pigments with these names actually contain natural earths; most of their ingredients today are synthetic. • The
chestnut tree has also been used since ancient times as a source brown dye. The bark of the tree, the leaves and the husk of the nuts have all been used to make dye. The leaves were used to make a beige or yellowish-brown dye, and in the Ottoman Empire the yellow-brown from chestnut leaves was combined with indigo blue to make shades of green. File:IronOxidePigmentUSGOV.jpg|
Iron oxide is the most common ingredient in brown pigments LimoniteUSGOV.jpg|
Limonite is a form of yellowish iron ore. A clay of limonite rich in iron oxide is the source of raw sienna and burnt sienna. File:Terra ombra naturale umber.jpg|Natural or raw
umber pigment is clay rich in
iron oxide and
manganese File:Pigment sienna burnt iconofile.jpg|Burnt
sienna pigment, from the region around
Siena in
Tuscany Brown eyes With few exceptions, all mammals have brown or darkly-pigmented irises. In humans, brown eyes result from a relatively high concentration of
melanin in the
stroma of the iris, which causes light of both shorter and longer wavelengths to be absorbed and in many parts of the world, it is nearly the only iris color present. Dark pigment of brown eyes is most common in
East Asia,
Central Asia,
Southeast Asia,
South Asia,
West Asia,
Oceania,
Africa,
Americas, etc. as well as parts of
Eastern Europe and
Southern Europe. The majority of people in the world overall have dark brown eyes. Brown irises range from highly pigmented, dark brown (almost black) eyes, to very light, almost amber or hazel irises composed partially of
lipochrome. of Light or medium-pigmented brown eyes are common in
Europe,
Afghanistan,
Pakistan and
Northern India, as well as some parts of the
Middle East, and can also be found in populations in
East Asia and
Southeast Asia, but are proportionally rare. (See
eye color). File:Epicanthic KR03.jpg|A dark brown iris is most common in
East Asia,
Southeast Asia, and
South Asia File:Picture of brown eyes.jpg|Medium brown iris File:Human eye with limbal ring, anterior view.jpg|Light brown irises can also be found in
East Asia and
Southeast Asia, but are relatively rare File:Hazel eyes S7307583.jpg|A light brown iris is most common in
North Africa,
Eastern Europe, the
Americas and
West Asia Brown hair Brown is the second most common color of human hair, after black. It is caused by higher levels of the natural dark pigment
eumelanin, and lower levels of the pale pigment
pheomelanin. Brown eumelanin is more common among Europeans, while black eumelanin is more often found in the hair on non-Europeans. A small amount of black eumelanin, in the absence of other pigments, results in grey hair. A small amount of brown eumelanin in the absence of other pigments results in blond hair. File:Brunette red lipstick.jpg|Brunette comes from
brune, the French term for a woman with brown hair File:Nadeeka Perera.jpg|Brown hair with highlights.
Nadeeka Perera, a fashion model File:Susan Sarandon 3 by David Shankbone.jpg|
Auburn hair is a reddish brown. This is actress
Susan Sarandon File:Yvonne Catterfeld.jpg|Chestnut color hair also has a reddish tint, but is less red and more brown than auburn hair. This is German singer
Yvonne Catterfeld Brown skin A majority of people in the world have skin that is a shade of brown, from a very light honey brown or a golden brown, to a copper or bronze color, to a coffee color or a dark chocolate brown. Skin color and race are not the same; many people classified as "white" or "black" actually have skin that is a shade of brown. Brown skin is caused by
melanin, a natural pigment which is produced within the skin in cells called
melanocytes. Skin pigmentation in humans evolved to primarily regulate the amount of
ultraviolet radiation penetrating the skin, controlling its biochemical effects. Natural skin color can darken as a result of
tanning due to exposure to sunlight. The leading theory is that skin color adapts to intense sunlight irradiation to provide partial protection against the
ultraviolet fraction that produces damage and thus mutations in the
DNA of the skin cells. There is a correlation between the geographic distribution of ultraviolet radiation (UVR) and the distribution of indigenous skin pigmentation around the world. Darker-skinned populations are found in the regions with the most ultraviolet, closer to the equator, while lighter skinned populations live closer to the poles, with less UVR, though immigration has changed these patterns. While
white and
black are commonly used to describe racial groups,
brown is rarely used, because it crosses all racial lines. In
Brazil, the Portuguese word
pardo, which can mean different shades of brown, is used to refer to multiracial people. The Brazilian Institute of Geography and Statistics (IBGE) asks people to identify themselves as
branco (white),
pardo (brown),
negro (black), or
amarelo (yellow). In 2008 43.8 percent of the population identified themselves as pardo. (See
human skin color). File:Elderly Gambian woman face portrait.jpg|An elderly woman from Gambia File:Flickr - DavidDennisPhotos.com - Man at Ruins in Cairo.jpg|A man from Egypt File:Gisele Bundchen2 cropped.jpg|Brazilian model
Gisele Bundchen File:Sera Monastery13.jpg|A man from Tibet File:Peruvian woman in hat smiling.jpg|A young woman from Peru
Soil The thin top layer of the Earth's crust on land is largely made up of
soil colored different shades of brown. Good soil is composed of about forty-five percent minerals, twenty-five percent water, twenty-five percent air, and five percent organic material, living and dead. Half the color of soil comes from minerals it contains; soils containing iron turn yellowish or reddish as the iron oxidizes. Manganese, nitrogen and sulfur turn brownish or blackish as they decay naturally. Rich and fertile soils tend to be darker in color; the deeper brown color of fertile soil comes from the decomposing of the organic matter. Dead leaves and roots become black or brown as they decay. Poorer soils are usually paler brown in color, and contain less water or organic matter. •
Mollisols are the soil type found under grassland in the
Great Plains of America, the
Pampas in Argentina and the Russian Steppes. The soil is 60–80 centimeters deep and is rich in nutrients and organic matter. •
Loess is a type of pale yellow or buff soil, which originated as wind-blown silt. It is very fertile, but is easily eroded by wind or water. •
Peat is an accumulation of partially decayed vegetation, whose decomposition is slowed by water. Despite its dark brown color, it is infertile, but is useful as a fuel. File:Soil profile.png|A typical soil profile; dark-brown
topsoils, rich with organic matter, above reddish-brown lower layers File:Mollisol.jpg|A profile of layers of
Mollisols, the soil type found in the
Great Plains of the U.S., the
Pampas in Argentina, and the Russian Steppes File:Loess landscape china.jpg|A landscape of
loess soil in
Datong,
Shanxi, China. Loess originated as windblown silt. It is very fertile but erodes easily File:Peat-Stack in Ness, Outer Hebrides, Scotland.jpg|A stack of
peat cut from the Earth in the Outer
Hebrides,
Scotland. Peat is partially decayed vegetative matter
Mammals and birds A large number of mammals and predatory birds have a brown coloration. This sometimes changes seasonally, and sometimes remains the same year-round. This color is likely related to
camouflage, since the backdrop of some environments, such as the forest floor, is often brown, and especially in the spring and summertime when animals like the
snowshoe hare get brown fur. Most mammals are
dichromats and so do not easily distinguish brown fur from
green grass. • The
brown rat or
Norwegian rat (
Rattus norvegicus) is one of the best known and most common
rats. • The
brown bear (
Ursus arctos) is a large
bear distributed across much of northern
Eurasia and
North America. • The
ermine (
Mustela erminea) has a brown back in summer, or year-round in the southern reaches of its range. File:Brown bear.jpg|The
brown bear is found across Eurasia and North America File:Tawny owl at night (42511916510).jpg|The
tawny owl. The color
tawny takes its name from the old French word
tané, which means to tan leather. The same word is the root of suntan and the color tan File:Lepus americanus 5459 cropped.jpg|The fur of the
snowshoe hare is brown in the summer and turns white in winter, as a form of all-season natural
camouflage File:Camelcalf-feeding.jpg|
Camel is an effective color for camouflage in the
Sahara desert, and is also a popular color for blankets and winter overcoats
Biology • The solid waste excreted by human beings and many other animals is characteristically brown in color due to the presence of
bilirubin, a byproduct of destruction of
red blood cells. == Brown in culture ==