Han Purple
Encyclopedia
Han purple and Han blue (also called Chinese purple and Chinese blue) are synthetic barium
copper
silicate
pigments that were developed in China
at least 2,000 years ago.
Han purple and Han blue were used in ancient and imperial China from the Western Zhou
period (1207-771 BC) until the end of the Han dynasty
(c. 220 AD).
was the only natural blue pigment used in early China. Early China seems not to have used a natural purple pigment and was the first to develop a synthetic one.
Han blue in its pure form is, as the name suggests, blue.
Han purple in its pure form is actually a dark blue, that is close to electric indigo
. It is a purple
in the way the term is used in colloquial English
, i.e., it is a color between red
and blue
. It is not, however, a purple in the way the term is used in color theory
, i.e. a non-spectral color between red
and violet
on the line of purples on the CIE chromaticity diagram. Perhaps the most accurate designation for the color would be to call it Han indigo, although it could also be regarded as a bright shade of ultramarine
(classifying ultramarine as a color and not a pigment).
The purple color seen in samples of Han purple is created by the presence of red copper (I) oxide (Cu2O) which is formed when Han purple decomposes (the red and blue making purple). The decomposition of Han purple to form copper (I) oxide is
Above 1050 °C, the CuO copper (II) oxide breaks down to copper (I) oxide:
, copper
, silicon
, and oxygen
). However, they differ in their formula, structure and chemical properties.
BaCuSi2O6.
Han purple has a layered structure
with isolated 4-ring silicates, and contains a copper-copper bond which makes the compound
more unstable than Han blue (metal-metal bonds are rare)
Han blue, like Han purple, has a layered structure with silicate forming the structural framework. However, Han blue is more stable because of structural features such as
and thermally less stable than Han blue. It fades and decomposes in dilute acid
. Han purple starts to decompose at temperatures more than 1050 - 1100 °C and forms a green-black glass at around 1200 °C.
It becomes more purplish when ground.
Production seems to have been focused in northern China, around 200–300 km north of the city of Xian
. This is the area with large deposits of raw materials. There are no written records about the production of Han purple or Han blue and so information about manufacture has been achieved through experimentation.
, a copper mineral and a lead salt. It is unknown whether minerals were used in their natural form or were pre-treated, though there is no evidence as yet of pre-treatment.
The barium source was either witherite
(BaCO3) or baryte (BaSO4). The rarity of witherite may favour baryte as the most likely source. Baryte has a slower decomposition rate and so favors Han blue production. Witherite conversely favors Han purple. In the use of baryte, lead salts (lead carbonate
or lead oxide
) would have been needed to increase yield. Lead has been detected in association with Han purple and Han blue
Lead acts as a catalyst in the decomposition of barium minerals and as a flux
. The amount of lead is important. Experiments show that too much lead (more than 5%) causes partial melting and glass formation above 1000 °C.
The role of lead is
is
The solid state reaction to create barium copper silicates starts at roughly 900 °C. Han purple is formed fastest. Han blue forms when there is an excess of silica and a longer reaction time allowed for. Early Chinese manufacture generally produced a mixture of Han blue and Han purple particles in various ratios, but pure colors were sometimes manufactured. Han blue could have been brought to a melt, but Han purple does not form a homogeneous
melt so it would have had to use a sintering
process.
Prolonged firing causes Han purple to break down and form Han blue:
The temperature needed to be high (around 900-1000 °C) and kept at that temperature for long periods. Han purple is thermally sensitive and so temperature control for producing Han purple needed to be fairly constant (±50 °C). Han blue is thermally less sensitive.
Under the right conditions, the manufacture of Han purple would have taken around 10–24 hours, while Han blue would have taken twice as long.
Temperature would have been controlled by testing of firing materials, the size, shape and material of the kiln
, and the control of the environment. Technology for achieving and maintaining high temperatures would have been known from metal and ceramic production e.g. the potential use of twin bellows as used in metal production.
in the position of Han blue's barium (BaCuSi4O10). The similarities lead some to suggest that Han blue was based on Egyptian Blue knowledge, which had travelled east along the Silk Road
. Independent innovation in China would still have been needed to replace calcium with barium (the Han pigments start to form at 100-200 °C higher than Egyptian blue).
The alternative suggestions are
The use of quartz, barium and lead components in ancient Chinese glass
and Han purple and Han blue has been used to suggest a connection between glass making and the manufacture of pigments, and to argue for independent Chinese invention. It has been argued that Taoist alchemists
developed Han purple from their knowledge of glass making.
The increase and decrease of barium glasses, and Han purple and Han blue, follow similar patterns. Both peaked in the Han dynasty
, declining afterwards. Pre-Han to Tang
dynasties see a shift from lead-barium-silicate type glass to lead-soda-lime glass. The reason for decline is debatable. Liu et al. attribute the decline to the decline of Taoism when Confucianism
was introduced, since they link pigment manufacture to the ideology of Taoism. Berke (2007) believes that political changes stopped the distribution of the pigments as the Chinese Empire was split at the end of the Han period.
) periods, and Han purple in later periods (c. 400 BC).
The Han pigments consist of varying combinations of blue, purple and colorless components. The grinding together of Han purple and Han blue would have allowed a variety of blue-purple shades.
The pigments were used for
period. The pigments are either present as compact bodies or in glazed layers.
. Han purple was used for the Terracotta Army
in the tomb of Emperor Qin Shi Huang
- the expense of producing Han purple and other pigments in such large quantities would have emphasised luxury and status. Han purple seems to have mostly been used on the trousers (pants) of the warriors. The pigment was bound to the terracotta surface with lacquer
.
The warriors were fired at the same temperature as that need for the manufacture of Han purple (950-1050 °C) and so the same kilns may have been used for both processes.
There is no evidence of Han blue being used for the warriors (azurite
was used for the blue).
, Jiangsu
Province and in the Han dynasty Yangling tombs of Emperor Liuqi
and his Empress (156-141 BC).
dark grey pottery vessels.
Han purple fades in acid, so colorless particles found in pigments containing Han blue and Han purple may be particles which were originally purple but which faded in acidic conditions in burial.
In addition, Han blue has fungicidal properties and so preserves better. Han purple reacts with oxalic acid
to form BaCu(C2O4)2. The light blue color of this salt may explain the light blue color of some of the Terracotta Warriors' trousers - the color resulting from the presence of oxalate
-excreting lichens.
Barium
Barium is a chemical element with the symbol Ba and atomic number 56. It is the fifth element in Group 2, a soft silvery metallic alkaline earth metal. Barium is never found in nature in its pure form due to its reactivity with air. Its oxide is historically known as baryta but it reacts with...
copper
Copper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...
silicate
Silicate
A silicate is a compound containing a silicon bearing anion. The great majority of silicates are oxides, but hexafluorosilicate and other anions are also included. This article focuses mainly on the Si-O anions. Silicates comprise the majority of the earth's crust, as well as the other...
pigments that were developed in China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
at least 2,000 years ago.
Han purple and Han blue were used in ancient and imperial China from the Western Zhou
Western Zhou
The Western Zhōu period was the first half of the Zhou Dynasty of ancient China. It began when King Wu of Zhou overthrew the Shang Dynasty at the Battle of Muye. C.H...
period (1207-771 BC) until the end of the Han dynasty
Han Dynasty
The Han Dynasty was the second imperial dynasty of China, preceded by the Qin Dynasty and succeeded by the Three Kingdoms . It was founded by the rebel leader Liu Bang, known posthumously as Emperor Gaozu of Han. It was briefly interrupted by the Xin Dynasty of the former regent Wang Mang...
(c. 220 AD).
Color
AzuriteAzurite
Azurite is a soft, deep blue copper mineral produced by weathering of copper ore deposits. It is also known as Chessylite after the type locality at Chessy-les-Mines near Lyon, France...
was the only natural blue pigment used in early China. Early China seems not to have used a natural purple pigment and was the first to develop a synthetic one.
Han blue in its pure form is, as the name suggests, blue.
Han purple in its pure form is actually a dark blue, that is close to electric indigo
Indigo
Indigo is a color named after the purple dye derived from the plant Indigofera tinctoria and related species. The color is placed on the electromagnetic spectrum between about 420 and 450 nm in wavelength, placing it between blue and violet...
. It is a purple
Purple
Purple is a range of hues of color occurring between red and blue, and is classified as a secondary color as the colors are required to create the shade....
in the way the term is used in colloquial English
English language
English is a West Germanic language that arose in the Anglo-Saxon kingdoms of England and spread into what was to become south-east Scotland under the influence of the Anglian medieval kingdom of Northumbria...
, i.e., it is a color between red
Red
Red is any of a number of similar colors evoked by light consisting predominantly of the longest wavelengths of light discernible by the human eye, in the wavelength range of roughly 630–740 nm. Longer wavelengths than this are called infrared , and cannot be seen by the naked eye...
and blue
Blue
Blue is a colour, the perception of which is evoked by light having a spectrum dominated by energy with a wavelength of roughly 440–490 nm. It is considered one of the additive primary colours. On the HSV Colour Wheel, the complement of blue is yellow; that is, a colour corresponding to an equal...
. It is not, however, a purple in the way the term is used in color theory
Color theory
In the visual arts, color theory is a body of practical guidance to color mixing and the visual impacts of specific color combinations. Although color theory principles first appeared in the writings of Leone Battista Alberti and the notebooks of Leonardo da Vinci , a tradition of "colory theory"...
, i.e. a non-spectral color between red
Red
Red is any of a number of similar colors evoked by light consisting predominantly of the longest wavelengths of light discernible by the human eye, in the wavelength range of roughly 630–740 nm. Longer wavelengths than this are called infrared , and cannot be seen by the naked eye...
and violet
Violet (color)
As the name of a color, violet is synonymous with a bluish purple, when the word "purple" is used in the common English language sense of any color between blue and red, not including either blue or red...
on the line of purples on the CIE chromaticity diagram. Perhaps the most accurate designation for the color would be to call it Han indigo, although it could also be regarded as a bright shade of ultramarine
Ultramarine
Ultramarine is a blue pigment consisting primarily of a double silicate of aluminium and sodium with some sulfides or sulfates, and occurring in nature as a proximate component of lapis lazuli...
(classifying ultramarine as a color and not a pigment).
The purple color seen in samples of Han purple is created by the presence of red copper (I) oxide (Cu2O) which is formed when Han purple decomposes (the red and blue making purple). The decomposition of Han purple to form copper (I) oxide is
- 3 BaCuSi2O6 → BaCuSi4O10 + 2 BaSiO3 + 2 CuO
Above 1050 °C, the CuO copper (II) oxide breaks down to copper (I) oxide:
- 4 CuO → 2 Cu2O + O2
Chemistry
Both Han purple and Han blue are barium copper silicates (containing bariumBarium
Barium is a chemical element with the symbol Ba and atomic number 56. It is the fifth element in Group 2, a soft silvery metallic alkaline earth metal. Barium is never found in nature in its pure form due to its reactivity with air. Its oxide is historically known as baryta but it reacts with...
, copper
Copper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...
, silicon
Silicon
Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...
, and oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
). However, they differ in their formula, structure and chemical properties.
Han purple
Han purple has the chemical formulaChemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....
BaCuSi2O6.
Han purple has a layered structure
Chemical structure
A chemical structure includes molecular geometry, electronic structure and crystal structure of molecules. Molecular geometry refers to the spatial arrangement of atoms in a molecule and the chemical bonds that hold the atoms together. Molecular geometry can range from the very simple, such as...
with isolated 4-ring silicates, and contains a copper-copper bond which makes the compound
Chemical compound
A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...
more unstable than Han blue (metal-metal bonds are rare)
Han blue
Han blue has the chemical formula BaCuSi4O10. In 1993, it was discovered to occur naturally as the rare mineral effenbergerite.Han blue, like Han purple, has a layered structure with silicate forming the structural framework. However, Han blue is more stable because of structural features such as
- It is more silica-rich
- Each 4-ring silicate if linked to four others in the adjacent level, in a zig zag pattern.
- The copper ions are very strongly contained within the stable silicate structure.
Chemical and physical properties
Han purple and blue are similar in many of their physical properties, which allows them to be mixed, but they differ in their chemical properties.Han purple
Han purple is chemicallyChemical stability
Chemical stability when used in the technical sense in chemistry, means thermodynamic stability of a chemical system.Thermodynamic stability occurs when a system is in its lowest energy state, or chemical equilibrium with its environment. This may be a dynamic equilibrium, where individual atoms...
and thermally less stable than Han blue. It fades and decomposes in dilute acid
Acid
An acid is a substance which reacts with a base. Commonly, acids can be identified as tasting sour, reacting with metals such as calcium, and bases like sodium carbonate. Aqueous acids have a pH of less than 7, where an acid of lower pH is typically stronger, and turn blue litmus paper red...
. Han purple starts to decompose at temperatures more than 1050 - 1100 °C and forms a green-black glass at around 1200 °C.
It becomes more purplish when ground.
Han blue
Han blue is more chemically and thermally stable. It does not break down in dilute acids and becomes more bluish when ground.Manufacture
Manufacturing depends on the raw materials, their ratios, fluxes, temperature, atmosphere and reaction time.Production seems to have been focused in northern China, around 200–300 km north of the city of Xian
Xi'an
Xi'an is the capital of the Shaanxi province, and a sub-provincial city in the People's Republic of China. One of the oldest cities in China, with more than 3,100 years of history, the city was known as Chang'an before the Ming Dynasty...
. This is the area with large deposits of raw materials. There are no written records about the production of Han purple or Han blue and so information about manufacture has been achieved through experimentation.
Raw materials
The raw materials needed are a barium mineral, quartzQuartz
Quartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...
, a copper mineral and a lead salt. It is unknown whether minerals were used in their natural form or were pre-treated, though there is no evidence as yet of pre-treatment.
The barium source was either witherite
Witherite
Witherite is a barium carbonate mineral, BaCO3, in the aragonite group. Witherite crystallizes in the orthorhombic system and virtually always is twinned. The mineral is colorless, milky white, grey, pale yellow, green, to pale brown. The specific gravity is 4.3, which is high for a translucent...
(BaCO3) or baryte (BaSO4). The rarity of witherite may favour baryte as the most likely source. Baryte has a slower decomposition rate and so favors Han blue production. Witherite conversely favors Han purple. In the use of baryte, lead salts (lead carbonate
Lead carbonate
Lead carbonate is the chemical compound PbCO3. It is prepared industrially from lead acetate and carbon dioxide.It occurs naturally as the mineral cerussite.-Basic lead carbonates:...
or lead oxide
Lead oxide
Lead oxide may refer to:* Lead oxide, PbO, litharge, massicot* Lead oxide, Pb3O4, minium, red lead* Lead dioxide , PbO2Less common lead oxides are:* Lead oxide, Pb2O3, lead sesquioxide...
) would have been needed to increase yield. Lead has been detected in association with Han purple and Han blue
Lead acts as a catalyst in the decomposition of barium minerals and as a flux
Ceramic flux
A ceramic flux functions by promoting glass formation in clay bodies and glazes. Fluxes are used in glazes to lower the high melting point of silica. The most commonly used fluxes in a ceramic glaze are lead, boric, soda, potassium, lithium, calcium, magnesium, barium, zinc, and strontium...
. The amount of lead is important. Experiments show that too much lead (more than 5%) causes partial melting and glass formation above 1000 °C.
The role of lead is
- BaSO4 + PbO ↔ PbSO4 + BaO
The manufacturing process
The production for Han blue using witheriteWitherite
Witherite is a barium carbonate mineral, BaCO3, in the aragonite group. Witherite crystallizes in the orthorhombic system and virtually always is twinned. The mineral is colorless, milky white, grey, pale yellow, green, to pale brown. The specific gravity is 4.3, which is high for a translucent...
is
- Cu2(CO3)(OH)2 + 8 SiO2 + 2 BaCO3 → 2 BaCuSi4O10 + 3 CO2 + H2O
The solid state reaction to create barium copper silicates starts at roughly 900 °C. Han purple is formed fastest. Han blue forms when there is an excess of silica and a longer reaction time allowed for. Early Chinese manufacture generally produced a mixture of Han blue and Han purple particles in various ratios, but pure colors were sometimes manufactured. Han blue could have been brought to a melt, but Han purple does not form a homogeneous
Homogeneous (chemistry)
A substance that is uniform in composition is a definition of homogeneous. This is in contrast to a substance that is heterogeneous.The definition of homogeneous strongly depends on the context used. In Chemistry, a homogeneous suspension of material means that when dividing the volume in half, the...
melt so it would have had to use a sintering
Sintering
Sintering is a method used to create objects from powders. It is based on atomic diffusion. Diffusion occurs in any material above absolute zero, but it occurs much faster at higher temperatures. In most sintering processes, the powdered material is held in a mold and then heated to a temperature...
process.
Prolonged firing causes Han purple to break down and form Han blue:
- 3 BaCuSi2O6 → BaCuSi4O10 + 2 BaSiO3 + 2 CuO
The temperature needed to be high (around 900-1000 °C) and kept at that temperature for long periods. Han purple is thermally sensitive and so temperature control for producing Han purple needed to be fairly constant (±50 °C). Han blue is thermally less sensitive.
Under the right conditions, the manufacture of Han purple would have taken around 10–24 hours, while Han blue would have taken twice as long.
Temperature would have been controlled by testing of firing materials, the size, shape and material of the kiln
Kiln
A kiln is a thermally insulated chamber, or oven, in which a controlled temperature regime is produced. Uses include the hardening, burning or drying of materials...
, and the control of the environment. Technology for achieving and maintaining high temperatures would have been known from metal and ceramic production e.g. the potential use of twin bellows as used in metal production.
Comparison
| Han purple | Han blue | |
|---|---|---|
| Chemical formula | BaCuSi2O6 | BaCuSi4O10 |
| Minimum temperature for production | 900-1000 °C | c. 1000 °C |
| Manufacture time | 10–24 hours | 20–48 hours |
| Decomposition temperature | 1050-1100 °C | >1200 °C |
| Thermally stable? | No | Yes |
| Stable in acid? | No | Yes |
| Color increase when ground? | Yes | Yes |
Han blue and Egyptian blue
Han blue and Egyptian blue have the same basic structure and have very similar properties. The difference is that Egyptian blue (CaCuSi4O10) has calciumCalcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
in the position of Han blue's barium (BaCuSi4O10). The similarities lead some to suggest that Han blue was based on Egyptian Blue knowledge, which had travelled east along the Silk Road
Silk Road
The Silk Road or Silk Route refers to a historical network of interlinking trade routes across the Afro-Eurasian landmass that connected East, South, and Western Asia with the Mediterranean and European world, as well as parts of North and East Africa...
. Independent innovation in China would still have been needed to replace calcium with barium (the Han pigments start to form at 100-200 °C higher than Egyptian blue).
The alternative suggestions are
- That earlier alkali metal glazing techniques were based on knowledge from Egypt, but that the copper silicate pigments (Egyptian blue and Han blue) developed from these glazes in two independent areas: Egypt and China.
- Alternatively, that examples of Han blue predate the official Silk Road and therefore that development was completely independent.
A Chinese invention? Links with glass making
The case against links with Egyptian blue includes the absence of lead in Egyptian blue and the lack of examples of Egyptian blue in China.The use of quartz, barium and lead components in ancient Chinese glass
Ancient Chinese glass
Ancient Chinese glass refers to all types of glass manufactured in China prior to the Qing Dynasty . In Chinese history, glass played a peripheral role in the arts and crafts, when compared to ceramics and metal work. The limited archaeological distribution and use of glass objects are evidence of...
and Han purple and Han blue has been used to suggest a connection between glass making and the manufacture of pigments, and to argue for independent Chinese invention. It has been argued that Taoist alchemists
Alchemy
Alchemy is an influential philosophical tradition whose early practitioners’ claims to profound powers were known from antiquity. The defining objectives of alchemy are varied; these include the creation of the fabled philosopher's stone possessing powers including the capability of turning base...
developed Han purple from their knowledge of glass making.
The increase and decrease of barium glasses, and Han purple and Han blue, follow similar patterns. Both peaked in the Han dynasty
Han Dynasty
The Han Dynasty was the second imperial dynasty of China, preceded by the Qin Dynasty and succeeded by the Three Kingdoms . It was founded by the rebel leader Liu Bang, known posthumously as Emperor Gaozu of Han. It was briefly interrupted by the Xin Dynasty of the former regent Wang Mang...
, declining afterwards. Pre-Han to Tang
Tang Dynasty
The Tang Dynasty was an imperial dynasty of China preceded by the Sui Dynasty and followed by the Five Dynasties and Ten Kingdoms Period. It was founded by the Li family, who seized power during the decline and collapse of the Sui Empire...
dynasties see a shift from lead-barium-silicate type glass to lead-soda-lime glass. The reason for decline is debatable. Liu et al. attribute the decline to the decline of Taoism when Confucianism
Confucianism
Confucianism is a Chinese ethical and philosophical system developed from the teachings of the Chinese philosopher Confucius . Confucianism originated as an "ethical-sociopolitical teaching" during the Spring and Autumn Period, but later developed metaphysical and cosmological elements in the Han...
was introduced, since they link pigment manufacture to the ideology of Taoism. Berke (2007) believes that political changes stopped the distribution of the pigments as the Chinese Empire was split at the end of the Han period.
Uses in cultural contexts
Han blue seems to have been favored in earlier (ZhouZhou Dynasty
The Zhou Dynasty was a Chinese dynasty that followed the Shang Dynasty and preceded the Qin Dynasty. Although the Zhou Dynasty lasted longer than any other dynasty in Chinese history, the actual political and military control of China by the Ji family lasted only until 771 BC, a period known as...
) periods, and Han purple in later periods (c. 400 BC).
The Han pigments consist of varying combinations of blue, purple and colorless components. The grinding together of Han purple and Han blue would have allowed a variety of blue-purple shades.
The pigments were used for
- Beads (from late Western Zhou periodZhou DynastyThe Zhou Dynasty was a Chinese dynasty that followed the Shang Dynasty and preceded the Qin Dynasty. Although the Zhou Dynasty lasted longer than any other dynasty in Chinese history, the actual political and military control of China by the Ji family lasted only until 771 BC, a period known as...
(1201-771 BC) ) - Octagonal sticks (from Warring States periodWarring States PeriodThe Warring States Period , also known as the Era of Warring States, or the Warring Kingdoms period, covers the Iron Age period from about 475 BC to the reunification of China under the Qin Dynasty in 221 BC...
) - The Terracotta ArmyTerracotta ArmyThe Terracotta Army or the "Terra Cotta Warriors and Horses", is a collection of terracotta sculptures depicting the armies of Qin Shi Huang, the first Emperor of China...
(Qin dynastyQin DynastyThe Qin Dynasty was the first imperial dynasty of China, lasting from 221 to 207 BC. The Qin state derived its name from its heartland of Qin, in modern-day Shaanxi. The strength of the Qin state was greatly increased by the legalist reforms of Shang Yang in the 4th century BC, during the Warring...
) - Painted figurines (Han dynastyHan DynastyThe Han Dynasty was the second imperial dynasty of China, preceded by the Qin Dynasty and succeeded by the Three Kingdoms . It was founded by the rebel leader Liu Bang, known posthumously as Emperor Gaozu of Han. It was briefly interrupted by the Xin Dynasty of the former regent Wang Mang...
) - Ceramic vessels (Han dynasty)
- Metal objects (Han dynasty)
- Wall paintings (Han dynasty)
Beads
Some of the earliest examples of the use of the Han pigments are beads which date back to the Western ZhouZhou Dynasty
The Zhou Dynasty was a Chinese dynasty that followed the Shang Dynasty and preceded the Qin Dynasty. Although the Zhou Dynasty lasted longer than any other dynasty in Chinese history, the actual political and military control of China by the Ji family lasted only until 771 BC, a period known as...
period. The pigments are either present as compact bodies or in glazed layers.
Octagonal sticks
These are compact bodies (solid sticks/rods) with shades ranging from light blue to dark purple. The range of colors is dues to varying proportions of Han blue, Han purple and colorless material. It is thought that they were pigment sticks which were traded then ground to be used as pigment bases in paints. It has also been suggested that they are of importance themselves, as ceremonial or bureaucratic items of importance.Terracotta army
Han purple and Han blue were first used in paints in the Qin dynastyQin Dynasty
The Qin Dynasty was the first imperial dynasty of China, lasting from 221 to 207 BC. The Qin state derived its name from its heartland of Qin, in modern-day Shaanxi. The strength of the Qin state was greatly increased by the legalist reforms of Shang Yang in the 4th century BC, during the Warring...
. Han purple was used for the Terracotta Army
Terracotta Army
The Terracotta Army or the "Terra Cotta Warriors and Horses", is a collection of terracotta sculptures depicting the armies of Qin Shi Huang, the first Emperor of China...
in the tomb of Emperor Qin Shi Huang
Qin Shi Huang
Qin Shi Huang , personal name Ying Zheng , was king of the Chinese State of Qin from 246 BC to 221 BC during the Warring States Period. He became the first emperor of a unified China in 221 BC...
- the expense of producing Han purple and other pigments in such large quantities would have emphasised luxury and status. Han purple seems to have mostly been used on the trousers (pants) of the warriors. The pigment was bound to the terracotta surface with lacquer
Lacquer
In a general sense, lacquer is a somewhat imprecise term for a clear or coloured varnish that dries by solvent evaporation and often a curing process as well that produces a hard, durable finish, in any sheen level from ultra matte to high gloss and that can be further polished as required...
.
The warriors were fired at the same temperature as that need for the manufacture of Han purple (950-1050 °C) and so the same kilns may have been used for both processes.
There is no evidence of Han blue being used for the warriors (azurite
Azurite
Azurite is a soft, deep blue copper mineral produced by weathering of copper ore deposits. It is also known as Chessylite after the type locality at Chessy-les-Mines near Lyon, France...
was used for the blue).
Painted pottery figurines
Smaller painted pottery figurines have been found e.g. the Western Han dynasty Chu Tombs, XuzhouXuzhou
Xuzhou , otherwise known as Pengcheng in ancient times, is a major city in and the fourth largest prefecture-level city of Jiangsu province, People's Republic of China...
, Jiangsu
Jiangsu
' is a province of the People's Republic of China, located along the east coast of the country. The name comes from jiang, short for the city of Jiangning , and su, for the city of Suzhou. The abbreviation for this province is "苏" , the second character of its name...
Province and in the Han dynasty Yangling tombs of Emperor Liuqi
Emperor Jing of Han
Emperor Jing of Han was an emperor of China in the Han Dynasty from 156 BC to 141 BC. His reign saw the limit and curtailment of power of feudal princes which resulted in the Rebellion of the Seven States in 154 BC. Emperor Jing managed to crush the revolt and princes were thereafter denied rights...
and his Empress (156-141 BC).
Ceramic vessels
Han blue and Han purple were used to decorate Han dynasty HuHu (vessel)
A hu is a type of pear-shaped ritual wine bronze vessel from ancient China. They would be placed in the grave of an ancestor as part of ritual banquet in order to ensure the good favor of that ancestor's spirit...
dark grey pottery vessels.
Metal objects
Bronze vessels in the Han dynasty, e.g. a bowl and top of a steamer were decorated with Han purple.Wall paintings
- A lintel and pedimentPedimentA pediment is a classical architectural element consisting of the triangular section found above the horizontal structure , typically supported by columns. The gable end of the pediment is surrounded by the cornice moulding...
from a Han dynasty tomb near Loyang were painted with a light blue pigment consisting of blue, purple and colorless components. - An Eastern Han period tomb mural painting in the XianXi'anXi'an is the capital of the Shaanxi province, and a sub-provincial city in the People's Republic of China. One of the oldest cities in China, with more than 3,100 years of history, the city was known as Chang'an before the Ming Dynasty...
area is one of the last examples of the use of synthetic barium copper silicate pigments (Han purple).
Preservation
Due to the instability of Han purple, it shows significant signs of weathering on archaeologically excavated artefacts. The copper (I) oxide formed in the decomposition of Han purple (see section on color) remains stable, but Han purple continues to deteriorate and so its purple color increases with time.Han purple fades in acid, so colorless particles found in pigments containing Han blue and Han purple may be particles which were originally purple but which faded in acidic conditions in burial.
In addition, Han blue has fungicidal properties and so preserves better. Han purple reacts with oxalic acid
Oxalic acid
Oxalic acid is an organic compound with the formula H2C2O4. This colourless solid is a dicarboxylic acid. In terms of acid strength, it is about 3,000 times stronger than acetic acid. Oxalic acid is a reducing agent and its conjugate base, known as oxalate , is a chelating agent for metal cations...
to form BaCu(C2O4)2. The light blue color of this salt may explain the light blue color of some of the Terracotta Warriors' trousers - the color resulting from the presence of oxalate
Oxalate
Oxalate , is the dianion with formula C2O42− also written 22−. Either name is often used for derivatives, such as disodium oxalate, 2C2O42−, or an ester of oxalic acid Oxalate (IUPAC: ethanedioate), is the dianion with formula C2O42− also written (COO)22−. Either...
-excreting lichens.
See also
- Egyptian blueEgyptian BlueEgyptian blue is chemically known as calcium copper silicate . It is a pigment used by Egyptians for thousands of years. It is considered to be the first synthetic pigment. The pigment was known to the Romans by the name caeruleum...
- Maya BlueMaya BlueMaya Blue is a unique bright azure blue pigment manufactured by cultures of pre-Columbian Mesoamerica, such as the Maya and Aztec.-Manufacture:...
- Prussian bluePrussian bluePrussian blue is a dark blue pigment with the idealized formula Fe718. Another name for the color Prussian blue is Berlin blue or, in painting, Parisian blue. Turnbull's blue is the same substance but is made from different reagents....
- Ancient Chinese glassAncient Chinese glassAncient Chinese glass refers to all types of glass manufactured in China prior to the Qing Dynasty . In Chinese history, glass played a peripheral role in the arts and crafts, when compared to ceramics and metal work. The limited archaeological distribution and use of glass objects are evidence of...
- List of colors
External links
- Raiders of the Lost Dimension (Magnet Lab, FSU) May 21, 2006
- Microscopic image of Han Purple (credit: Marcelo Jaime of MST-NHMFL)