Yellow is the color between green and orange on the spectrum of light. It is evoked by light with a dominant wavelength of roughly 575–585 nm. It is a primary color in subtractive color systems, used in painting or color printing. In the RGB color model, used to create colors on television and computer screens, yellow is a secondary color made by combining red and green at equal intensity. Carotenoids give the characteristic yellow color to autumn leaves, corn, canaries, daffodils, and lemons, as well as egg yolks, buttercups, and bananas. They absorb light energy and protect plants from photo damage in some cases. Sunlight has a slight yellowish hue when the Sun is near the horizon, due to atmospheric scattering of shorter wavelengths.
Ultramarine is a deep blue color pigment which was originally made by grinding lapis lazuli into a powder. Its lengthy grinding and washing process makes the natural pigment quite valuable—roughly ten times more expensive than the stone it comes from and as expensive as gold.
A pigment is a powder used to add color or change visual appearance. Pigments are completely or nearly insoluble and chemically unreactive in water or another medium; in contrast, dyes are colored substances which are soluble or go into solution at some stage in their use. Dyes are often organic compounds whereas pigments are often inorganic. Pigments of prehistoric and historic value include ochre, charcoal, and lapis lazuli.
Saponification is a process of cleaving esters into carboxylate salts and alcohols by the action of aqueous alkali. Typically aqueous sodium hydroxide solutions are used. It is an important type of alkaline hydrolysis. When the carboxylate is long chain, its salt is called a soap. The saponification of ethyl acetate gives sodium acetate and ethanol:
A lake pigment is a pigment made by precipitating a dye with an inert binder, or mordant, usually a metallic salt. Unlike vermilion, ultramarine, and other pigments made from ground minerals, lake pigments are organic. Manufacturers and suppliers to artists and industry frequently omit the lake designation in the name. Many lake pigments are fugitive because the dyes involved are not lightfast. Red lakes were particularly important in Renaissance and Baroque paintings; they were often used as translucent glazes to portray the colors of rich fabrics and draperies.
Ochre, or ocher in American English, is a natural clay earth pigment, a mixture of ferric oxide and varying amounts of clay and sand. It ranges in colour from yellow to deep orange or brown. It is also the name of the colours produced by this pigment, especially a light brownish-yellow. A variant of ochre containing a large amount of hematite, or dehydrated iron oxide, has a reddish tint known as "red ochre".
Umber is a natural earth pigment consisting of iron oxide and manganese oxide; it has a brownish color that can vary among shades of yellow, red, and green. Umber is considered one of the oldest pigments known to humans, first seen in Ajanta Caves in 200 BC – 600 AD. Umber's advantages are its highly versatile color, warm tone, and quick drying abilities. While some sources indicate that umber's name comes from its geographic origin in Umbria, other scholars suggest that it derives from the Latin word umbra, which means "shadow". The belief that its name derives from the word for shadow is fitting, as the color helps create shadows. The color is primarily produced in Cyprus. Umber is typically mined from open pits or underground mines and ground into a fine powder that is washed to remove impurities. In the 20th century, the rise of synthetic dyes decreased the demand for natural pigments such as umber.
Azo compounds are organic compounds bearing the functional group diazenyl.
Sudan I is an organic compound, typically classified as an azo dye. It is an intensely orange-red solid that is added to colourise waxes, oils, petrol, solvents, and polishes. Sudan I has also been adopted for colouring various foodstuffs, especially curry powder and chili powder, although the use of Sudan I in foods is now banned in many countries, because Sudan I, Sudan III, and Sudan IV have been classified as category 3 carcinogens by the International Agency for Research on Cancer. Sudan I is still used in some orange-coloured smoke formulations and as a colouring for cotton refuse used in chemistry experiments.
Phenazopyridine is a medication which, when excreted by the kidneys into the urine, has a local analgesic effect on the urinary tract. It is often used to help with the pain, irritation, or urgency caused by urinary tract infections, surgery, or injury to the urinary tract.
An acid dye is a dye that is typically applied to a textile at low pH. They are mainly used to dye wool, not cotton fabrics. Some acid dyes are used as food colorants, and some can also be used to stain organelles in the medical field.
Aniline Yellow is a yellow azo dye and an aromatic amine. It is a derivative of azobenzene. It has the appearance of an orange powder. Aniline Yellow was the first azo dye. it was first produced in 1861 by C. Mene. The second azo dye was Bismarck Brown in 1863. Aniline Yellow was commercialized in 1864 as the first commercial azo dye, a year after aniline black. It is manufactured from aniline.
2-Tolidine (orthotolidine, o-tolidine; not to be confused with o-toluidine) is an organic compound with the chemical formula (C6H4(CH3)NH2)2. Several isomers are known; the 3-tolidine derivative is also important commercially. It is a colorless compound although commercial samples are often colored. It is slightly soluble in water. It forms salts with acids, such as the hydrochloride, which is commercially available.
A urine test strip or dipstick is a basic diagnostic tool used to determine pathological changes in a patient's urine in standard urinalysis.
Officer and Laughing Girl, also known as Officer and a Laughing Girl, Officer With a Laughing Girl or, in Dutch, De Soldaat en het Lachende Meisje, was painted by the Dutch artist Johannes Vermeer in around 1657. It was painted in oil on canvas, typical of most Dutch artists of the time, and is 50.5 by 46 cm. It is now one of three pictures by Vermeer in The Frick Collection in New York
Woman Holding a Balance, also called Woman Testing a Balance, is an oil painting by Dutch Golden Age painter Johannes Vermeer, now in the National Gallery of Art in Washington, DC.
Lead-tin yellow is a yellow pigment, of historical importance in oil painting, sometimes called the "Yellow of the Old Masters" because of the frequency with which it was used by those famous painters.
A colorant is any substance that changes the spectral transmittance or reflectance of a material. Synthetic colorants are those created in a laboratory or industrial setting. The production and improvement of colorants was a driver of the early synthetic chemical industry, in fact many of today's largest chemical producers started as dye-works in the late 19th or early 20th centuries, including Bayer AG(1863). Synthetics are extremely attractive for industrial and aesthetic purposes as they have they often achieve higher intensity and color fastness than comparable natural pigments and dyes used since ancient times. Market viable large scale production of dyes occurred nearly simultaneously in the early major producing countries Britain (1857), France (1858), Germany (1858), and Switzerland (1859), and expansion of associated chemical industries followed. The mid-nineteenth century through WWII saw an incredible expansion of the variety and scale of manufacture of synthetic colorants. Synthetic colorants quickly became ubiquitous in everyday life, from clothing to food. This stems from the invention of industrial research and development laboratories in the 1870s, and the new awareness of empirical chemical formulas as targets for synthesis by academic chemists. The dye industry became one of the first instances where directed scientific research lead to new products, and the first where this occurred regularly.
Caput mortuum, also known as cardinal purple, is the name given to a purple variety of haematite iron oxide pigment, used in oil paints and paper dyes. Due to the cultural significance of its deep purple colour, it was very popular for painting the robes of religious figures and important personages, with its popularity peaking in the 18th and 19th centuries.
Red pigments are materials, usually made from minerals, used to create the red colors in painting and other arts. The color of red and other pigments is determined by the way it absorbs certain parts of the spectrum of visible light and reflects the others. The brilliant opaque red of vermillion, for example, results because vermillion reflects the major part of red light, but absorbs the blue, green and yellow parts of white light.
Color coordinates