Brazilin
Encyclopedia
Brazilin is a red pigment obtained from the wood of the brazilwood
family (Caesalpinia sp), and is also known as Natural Red 24. Brazilin has been used since at least the Middle Ages to dye
fabric, and has been used to make paints and inks as well. The specific color produced by the pigment depends on its manner of preparation: in an acidic solution brazilin will appear yellow, but in an alkaline preparation it will appear red. Brazilin is closely related to the blue-black dye haematoxylin
, having one less hydroxyl group. Brazilein is the name for the oxidised pigment.
(C. echinata) and sappanwood
(C. sappan). The sappanwood is found in India, Malaysia, and Sri Lanka, the latter being a major supplier of the wood to Europe during the early Middle Ages. Later, discovery of brazilwood in the new world led to its rise in popularity with the dye industry and eventually its over-exploitation. Brazilwood is now classified as an endangered species
.
(which produces a deep, purplish red) or a hot solution of alum
(which produces an orange-red color), either of which extracts the color better than plain water alone. To the lye extract, alum is added (or to the alum extract, lye) in order to fix the color, which will precipitate from the solution. The precipitate can be dried and powdered, and is a type of lake pigment
.
Like many lake pigments, the exact colors produced depends on the pH of the mixture and the fixative used. Aluminum mordants used with brazilin produce the standard red colors, while the use of a tin mordant, in the form of SnCl2 or SnCl4 added to the extract is capable of yielding a pink color.
An alternative preparation which produces a transparent red color involves soaking the brazilwood powder in glair or a solution of gum arabic
. Alum is added to help develop and fix the color, which can then be used as a transparent ink or paint.
As with haematoxylin
, brazilin can be used for staining cell nuclei in histological preparations when combined with aluminum. The nuclei are then colored red instead of blue.
Brazilwood
Caesalpinia echinata is a species of Brazilian timber tree in the pea family, Fabaceae. Common names include Brazilwood, Pau-Brasil, Pau de Pernambuco and Ibirapitanga . This plant has a dense, orange-red heartwood that takes a high shine, and it is the premier wood used for making bows for...
family (Caesalpinia sp), and is also known as Natural Red 24. Brazilin has been used since at least the Middle Ages to dye
Natural dye
Natural dyes are dyes or colorants derived from plants, invertebrates, or minerals. The majority of natural dyes are vegetable dyes from plant sources – roots, berries, bark, leaves, and wood — and other organic sources such as fungi and lichens....
fabric, and has been used to make paints and inks as well. The specific color produced by the pigment depends on its manner of preparation: in an acidic solution brazilin will appear yellow, but in an alkaline preparation it will appear red. Brazilin is closely related to the blue-black dye haematoxylin
Haematoxylin
Haematoxylin, hematoxylin, Natural Black 1, or C.I. 75290 is extracted from the heartwood of the logwood tree. When oxidized it forms haematein, a compound that forms strongly coloured complexes with certain metal ions, the most notable ones being Fe and Al salts. Metal-haematein complexes are used...
, having one less hydroxyl group. Brazilein is the name for the oxidised pigment.
Sources of brazilin
Many members of the genus Caesalpinia produce brazilin, including brazilwoodBrazilwood
Caesalpinia echinata is a species of Brazilian timber tree in the pea family, Fabaceae. Common names include Brazilwood, Pau-Brasil, Pau de Pernambuco and Ibirapitanga . This plant has a dense, orange-red heartwood that takes a high shine, and it is the premier wood used for making bows for...
(C. echinata) and sappanwood
Sappanwood
Caesalpinia sappan is a species of flowering tree in the legume family, Fabaceae, that is native to Southeast Asia and the Malay archipelago. Common names include Sappanwood, Sapanwood, and Suou . Sappanwood belongs to the same genus as Brazilwood , and was originally called "brezel wood" in...
(C. sappan). The sappanwood is found in India, Malaysia, and Sri Lanka, the latter being a major supplier of the wood to Europe during the early Middle Ages. Later, discovery of brazilwood in the new world led to its rise in popularity with the dye industry and eventually its over-exploitation. Brazilwood is now classified as an endangered species
Endangered species
An endangered species is a population of organisms which is at risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters...
.
Extraction and preparation
There are many ways to extract and prepare brazilin. A common recipe, developed in the Middle Ages, is to first powder the brazilwood, turning it into sawdust. Then, the powder can be soaked in lyeLye
Lye is a corrosive alkaline substance, commonly sodium hydroxide or historically potassium hydroxide . Previously, lye was among the many different alkalis leached from hardwood ashes...
(which produces a deep, purplish red) or a hot solution of alum
Alum
Alum is both a specific chemical compound and a class of chemical compounds. The specific compound is the hydrated potassium aluminium sulfate with the formula KAl2.12H2O. The wider class of compounds known as alums have the related empirical formula, AB2.12H2O.-Chemical properties:Alums are...
(which produces an orange-red color), either of which extracts the color better than plain water alone. To the lye extract, alum is added (or to the alum extract, lye) in order to fix the color, which will precipitate from the solution. The precipitate can be dried and powdered, and is a type of lake pigment
Lake pigment
A lake pigment is a pigment manufactured by precipitating a dye with an inert binder, usually a metallic salt. The word lake is a homonym of lake as body of water and does not refer to it....
.
Like many lake pigments, the exact colors produced depends on the pH of the mixture and the fixative used. Aluminum mordants used with brazilin produce the standard red colors, while the use of a tin mordant, in the form of SnCl2 or SnCl4 added to the extract is capable of yielding a pink color.
An alternative preparation which produces a transparent red color involves soaking the brazilwood powder in glair or a solution of gum arabic
Gum arabic
220px|thumb|right|Acacia gumGum arabic, also known as acacia gum, chaar gund, char goond, or meska, is a natural gum made of hardened sap taken from two species of the acacia tree; Acacia senegal and Acacia seyal...
. Alum is added to help develop and fix the color, which can then be used as a transparent ink or paint.
As with haematoxylin
Haematoxylin
Haematoxylin, hematoxylin, Natural Black 1, or C.I. 75290 is extracted from the heartwood of the logwood tree. When oxidized it forms haematein, a compound that forms strongly coloured complexes with certain metal ions, the most notable ones being Fe and Al salts. Metal-haematein complexes are used...
, brazilin can be used for staining cell nuclei in histological preparations when combined with aluminum. The nuclei are then colored red instead of blue.