Copper sulphate was a clever choice, police said, because it is not normally classified as a colourant so food control authorities do not usually test for it.
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In Italy, where black bread is known as pane al carbone vegetale, 12 bakeries have been accused of using 153 Carbon Black as a colourant in breads, BakeryandSnacks.
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During the fading, colourant molecules undergo various chemical processes which result in fading. When a UV-photon reacts with a molecule acting as colourant, the molecule is excited from the ground state to an excited state. The excited molecule is highly reactive and unstable. During the quenching of the molecule from excited state to ground state, atmospheric triplet oxygen reacts with the colourant molecule to form singlet oxygen and superoxide oxygen radical.
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Euxanthic acid is a xanthonoid glycoside, a conjugate of the aglycone euxanthone with glucuronic acid. Its magnesium salt is the primary colourant of the pigment Indian Yellow.
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Phototendering, i.e., photochemical tendering. As a result of UV light, the substrate material supplies hydrogen to the colourant molecules, reducing the colorant molecule. As the hydrogen is removed, the material undergoes oxidation.
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Dibromoanthanthrone is a scarlet or orange-red-hue synthetic organic colourant. It is an anthraquinone derivative, first synthesized in 1913 as a vat dye, C.I. Vat Orange 3 (C.I. 59300), and later on also as a pigment, C.I. Pigment Red 168.
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Nigrosene is an outdated trade name for a black dye made from oxidised aniline dispersed in water. It was used as a colourant in shoe polish until the 1940s, and as a dark stain for bedplates, brackets, crank handles, and wood. This name is no longer used in today's trading market.
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Photolysis, i.e., photochemical decomposition is a chemical reaction where the compound is broken down by the photons. This decomposition occurs when a photon of sufficient energy encounters a colorant molecule bond with a suitable dissociation energy. The reaction causes homolytic cleavage in the chromophoric system resulting the fading of the colourant.
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Photosensitization, i.e., photochemical sensitization. Exposing dyed cellulosic material, such as plant-based fibers, to sunlight allows dyes to remove hydrogen from the cellulose, resulting in photoreduction on the cellulosic substrate. Simultaneously, the colorant will undergo oxidation in the presence of the atmospheric oxygen, resulting in photo- oxidation of the colourant.
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Commercially produced mushy peas contain artificial colourants to make them green - without these the dish would be murky grey. Traditionally the controversial colourant Tartrazine (E102) had been used as one of the colourants, however as recently as 2019 major manufacturers were using a combination of Brilliant Blue FCF (E133) and Riboflavin (E101).
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Starting in the late Middle Ages, pitchblende was extracted from the Habsburg silver mines in Joachimsthal, Bohemia (now Jáchymov in the Czech Republic) and was used as a coloring agent in the local glassmaking industry. Martin Klaproth (1743–1817), who discovered uranium, later experimented with the use of the element as a glass colourant.
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Retrieved 2016-02-22. The scale insect Dactylopius coccus produces the brilliant red-coloured carminic acid to deter predators. Up to 100,000 scale insects need to be collected and processed to make a kilogram (2.2 lbs) of cochineal dye. A similar number of lac bugs are needed to make a kilogram of shellac, a brush-on colourant and wood finish.
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There have been many attempts to replace saffron with a cheaper dye. Saffron's usual substitutes in food--turmeric and safflower, among others--yield a garishly bright yellow that could hardly be confused with that of saffron. Saffron's main colourant is the carotenoid crocin; it has been discovered in the less tediously harvested--and hence less costly--gardenia fruit. Research in China is ongoing.
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Rubia was an economically important source of a red pigment in many regions of Asia, Europe and Africa. The genus name Rubia derives from the Latin ' meaning "red". The plant's roots contain an anthracene compound called alizarin that gives its red colour to a textile dye known as Rose madder. It was also used as a colourant, especially for paint, that is referred to as Madder lake.
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As a result, the color was eventually replaced by imported Prussian blue, a much more stable colour with its first commercial appearance in 1829 in the work of Keisai Eisen. The plant is also grown for its dye in northern China. Additional uses of the colourant include making preparatory designs on cloth before dyeing with other pigments. Commelinin is the blue pigment from the flowers of C. communis, is a metalloanthocyanin.
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Narthecium ossifragum, commonly known as bog asphodel, Lancashire asphodel or bastard asphodel, is a plant of Western Europe, found on wet, boggy moorlands up to about in elevation. It produces spikes of bright yellow flowers in summer. The bright orange fruits have been used as a colourant to replace saffron by Shetland Islanders.Richard Mabey Flora Britannica Despite the plant's English name, it is not particularly closely related to the true asphodels.
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C-phycocyanin (C-PC) can be used as a natural blue food colouring. This food colourant can only be used for low temperature prepared goods because of its inability to maintaining its blue colouring in high heats unless there is an addition of preservatives or sugars. The type of sugar is irrelevant, C-PC is stable when there is high sugar content. Knowing so, C-PC can be used for numerous types of foods, one of which being syrups.
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Rubia cordifolia was an economically important source of a red pigment in many regions of Asia, Europe and Africa. It was extensively cultivated from antiquity until the mid nineteenth century. The plant's roots contain an anthraquinone called purpurin (1,2,4-Trihydroxyanthraquinone) that gives its red colour as a textile dye It was also used as a colourant, especially for paint, that is referred to as Madder lake. The substance was also derived other species; Rubia tinctorum, also widely cultivated, and the Asiatic species Rubia argyi (H.
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Properties of phycobiliproteins, such as their natural antioxidant, anti-inflammatory, food colourant, strong pigment and anti-aging activities, have given them considerable potential for use in food, cosmetics and medicinal applications. They have also proven to be therapeutic in treating diseases such as Alzheimer's disease and cancer. Given their large range of applications and potential uses, researchers have been trying to find and develop ways to produce and purify phycobiliproteins to meet the growing demand for them. One such phycobiliprotein is C-phycocyanin (C-PC), which is found in spirulina.
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In addition to its use in the H&E; stain, haematoxylin is also a component of the Papanicolaou stain (or PAP stain) which is widely used in the study of cytology specimens. Although the stain is commonly called haematoxylin, the active colourant is the oxidized form haematein, which forms strongly coloured complexes with certain metal ions (commonly Fe(III) and Al(III) salts). In its pure form, haematoxylin is a colourless and crystalline solid, although commercial samples are typically light to dark-brown based on the level of impurities present.
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The relative amount of fading can be measured and studied by using standard test strips. In the workflow of the Blue Wool test, one reference strip set shall be stored protected from any exposure to light. Simultaneously, another equivalent test strip set is exposed under a light source defined in the standard. For example, if the lightfastness of the colourant is indicated to be 5 on the Blue Wool scale, it can be expected to fade by a similar amount as the strip number 5 in the Blue Wool test strip set.
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A colourant/colour additive (British spelling) or colorant/color additive (American spelling) is a substance that is added or applied in order to change the colour of a material or surface. Colourants can be used for many purposes including printing, painting, and for colouring many types of materials such as foods and plastics. Colourants work by absorbing varying amounts of light at different wavelengths (or frequencies) of its spectrum, transmitting (if translucent) or reflecting the remaining light in straight lines or scattered. Most colourants can be classified as dyes or pigments, or containing some combination of these.
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Pinder-Wilson 1991, 130 This technique was often combined with enamelling, the application of ground glass with a colourant, to traditional and new vessel forms, and represents the height of Islamic glassmaking.Carboni 2001, 323–325 Enamelling, a resurrection of older techniques, was first practiced in the Islamic world at Raqqa (Syria) during the late 12th century, but also spread to Cairo during Mamluk rule.Gudenrath 2006, 42 A study of various enamelled vessels, including beakers and mosque lamps, suggests that there are two subtle yet distinct firing practices, possibly representing two distinct production centres or glass-working traditions.
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Clay earth pigments such as burnt sienna often have a high lightfastness Lightfastness is a property of a colourant such as dye or pigment that describes how resistant to fading it is when exposed to light. Dyes and pigments are used for example for dyeing of fabrics, plastics or other materials and manufacturing paints or printing inks. The bleaching of the color is caused by the impact of ultraviolet radiation in the chemical structure of the molecules giving the color of the subject. The part of a molecule responsible for its color is called the chromophore.
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Ancient Roman pottery, mould-decorated terra sigillata bowl from Gaul (Metz in France) In sharp contrast to the archaeological usage, in which the term terra sigillata refers to a whole class of pottery, in contemporary ceramic art, 'terra sigillata' describes only a watery refined slip used to facilitate the burnishing of raw clay surfaces and used to promote carbon smoke effects, in both primitive low temperature firing techniques and unglazed alternative western-style Raku firing techniques. Terra sigillata is also used as a brushable decorative colourant medium in higher temperature glazed ceramic techniques.Garbsch, Jochen, Terra Sigillata. (1982) Ein Weltreich im Spiegel seines Luxusgeschirrs, Munich.
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For more thoroughly cleaning iron gall ink out of a fountain pen, sequential flushes of the pen with water, diluted vinegar or citric acid (to flush out residual iron gall compounds), water, diluted ammonia (if needed to flush out residual colour dye stains), then finally water are often recommended. The colour dye in these modern iron gall formulas functions as a temporary colourant to make these inks clearly visible whilst writing. The ferro-gallic compounds through a gradual oxidation process cause an observable gradual colour change to grey/black whilst these inks completely dry and makes the writing waterproof. The colour-changing property of the ink also depends on the properties of the used paper.
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Texts listing offerings to Egyptian temples would start with gold and silver, followed by precious stones (lapis lazuli) and then bronze, copper and other not so precious stones with glass mentioned together with the lapis lazuli. In this period it was rare and precious and its use largely restricted to the elite. Shortland 2007 The oldest glass ingot was discovered in the 1300 B.C. Egyptian Uluburun shipwreck off the coast of Turkey Production of raw glass occurred at primary workshops of which only 3 are known, all in Egypt: Amarna, Pi-Ramesses and Malkata.Walton et al 2009 At the first two sites cylindrical ceramic vessels with vitrified remains have been identified as glass cruciblesRehren & Push 1997Nicholson et al 1997 where the raw materials (quartz pebbles and plant ash) would be melted together with a colourant.
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