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9.8 The chemistry of art: 1. The earliest uses of colour
Extract from Chemistry Stage 6 Syllabus (Amended
October 2002), © Board of Studies, NSW.
[Edit: 27 Jun 08]
Prior Learning: Preliminary modules 8.2.1, 8.2.2, 8.3.4,
Background: One of the earliest technologies that humans invented was the making of paint. By using different coloured earth, or grinding soft rocks to a powder, early people could make pictures of different colours. The first use of minerals was for cave painting. The Egyptians used minerals in their cosmetics and for tomb painting. Australian Aboriginal painters used earth colours - reds, browns, and yellows, black and white - from ochres and other minerals.
Early humans used coloured pigments removed from the earth to paint their bodies and implements, and the caves in which they lived. Graves unearthed by archaeologists showed bodies covered in red pigment. Red was a colour associated with blood and symbolised life's meaning and end. The word haematite is derived from the Greek word haema meaning blood. As iron oxide (haematite) did not fade unlike vegetable dyes, people sought and mined the red pigment - haematite.
solve problems and perform a first hand investigation or process information from secondary sources to identify minerals that have been used as pigments and describe their chemical composition with particular reference to pigments available and used in traditional art by Aboriginal people
- A first-hand investigation could be performed by contacting local Aboriginal people and asking them to speak about the pigments their people have used for thousands of years. Ask if they can bring the rocks that have been traditionally used and show how they are treated to produce the pigments. If you are having difficulty finding people who can assist, try contacting the local Land Council. They may know of artists who would be available to speak. You may find that other material such as charcoal is also used.
- If the artist can't tell you about the chemical composition of the pigments, you may have to use secondary sources to find this information. The Encyclopedia of Aboriginal Australia would be a good place to start. Look up the word 'pigment' and 'ochre'. You could then try the Internet. Use a search engine and type words such as 'Aboriginal', 'pigment', 'ochre', 'chemistry'.
- When you have enough information you could process the information by putting it in a table with the headings, Pigment and Chemical composition. Another column could be Colour. Try to find out if colours were mixed and what colours were produced when this was done.
identify the sources of the pigments used in early history as readily available minerals
- The sources of pigments were the minerals found in coloured earth and soft rocks
- Examples of the minerals readily available as pigments included: gypsum, cerussite, stibnite, galena, graphite, cinnabar, haematite, malachite, azurite, orpiment.
Mineral Colour Chemical Formula gypsum white, grey CaSO4.2H2O cerussite white, grey PbCO3 stibnite lead-grey, blackish Sb2S3 galena lead-grey PbS graphite black C cinnabar red, brownish red HgS haematite earthy to bright red Fe2O3 malachite bright green Cu2(CO3)(OH)2 azurite azure blue to dark blue Cu3(CO3)2(OH)2 orpiment lemon yellow - brownish yellow As2S3 turquoise bluish green CuAl6(PO4)4(OH) 8 .4H2O
- The Aboriginal painters used earth colours. Red is a very important colour, especially in desert cultures and is widely valued. It came from a variety of ochres, usually mixtures of hydrated oxides of iron. Manganese oxide, crushed charcoal or charred bark provided the colour black, and white usually came from kaolin.
Mineral Colour Chemical Formula pyrolusite (manganese dioxide) iron grey, black streak MnO2 haematite (hydrated oxide of iron) red-brown to bright red Fe2O3 limonite yellow FeO(OH) kaolinite white Al2Si2O5 (OH)4 Information about Aboriginal mining can be found at Flinders Ranges Research
and National Museum of Australia, Canberra First Australians, Country.Mining in the Northern Flinders Ranges
The above websites do not list the chemical composition of the ochres but the one below does. Scroll down to pages 6,7 and 8 to find all the elements present in two ochres and how they analysed them. Submission to the Parliamentary Inquiry into Australia's Indigenous Arts Sector by Professor John Watling and Ms Rachel Green
process information from secondary sources to identify the chemical composition of identified cosmetics used in an ancient culture such as early Egyptian or Roman and use available evidence to assess the potential health risk associated with their use
- Choose whether you are going to investigate Egyptian, Roman or some other culture.
- Identify secondary sources of information, such as science references or the Internet. You might like to talk to the Art Department at your school as they may have suitable books that would be good secondary sources. Process the information by assessing the reliability of material found from different sources. Be aware that much material on the Internet has no quality control so it is good to check several different sites and books as well.
- To process the information identify the chemical composition. Use available evidence to assess the potential health risks. You might write down all the metals that you have found are in the cosmetics and beside each one list any health risk they would pose, especially when used on skin over prolonged periods.
Some useful information
The Egyptians used minerals in their cosmetics. They used red ochre (haematite) on their lips, and Kohl in elaborate eye make-up. Their cosmetic materials included black pigments such as stibnite (black antimony sulfide), and colourful copper minerals such as malachite, azurite and turquoise, while white cerussite (lead carbonate) was used as a highlighting cosmetic.
Prolonged use of these cosmetics containing heavy metals such as lead, copper and antimony was poisonous and also disfigured the skin. The advantage of haematite was that it was not poisonous.
outline the early uses of pigments for:
- cave drawings
- self-decoration including cosmetics
- preparation of the dead for burial
-
Early humans used pigments in their cave paintings. The
red in the paintings comes from red ochre (haematite),
the yellow from yellow ochre (limonite) and the black was
often from charcoal from their fires.
Aboriginal rock art
, UPDatesfrom DOWNUnder by Dr Ellen K Rudolph
and Dr Nicole Duplaix, Williamsburg, Virginia, USA. - People also used pigments for body paint. They used the red of haematite and the yellow of limonite. Elizabeth the First of England used cerussite or white lead as a face paint.
- In preparing the dead for burial, mineral pigments were used in many ways. In the Egyptian pharaoh Tutankhamen's tomb a small paint box was found containing powdered gypsum, orpiment, haematite and malachite. Vermilion made from cinnabar was used to paint red the sacred statue of Jupiter found in Roman temples.
explain why pigments used needed to be insoluble in most substances
- Most of the metal sulfides and oxides used as pigments were insoluble. This was advantageous as they were not easily removed when exposed to rain or ground water in the case of cave or rock paintings. While in hot climates, cosmetics made from insoluble minerals would not dissolve in perspiration.
outline the processes used and the chemistry involved to prepare and attach pigments to surfaces in a named example of medieval or earlier artwork
- The vivid blue pigment ultramarine is extracted from the stone lapis lazuli. This was used by medieval European artists for the virgin's cloak.
- A method for extracting this blue pigment was developed in the 13th century. The process consisted of mixing the ground lapis lazuli stone with melted wax, resins and oils, then wrapping the mixture within cloth and kneading it under a dilute lye solution of potassium carbonate. The blue particles formed a precipitate and the impurities were collected in the wax, resin and oil.
explain that colour can be obtained through pigments spread on a surface layer (e.g. paints) or mixed with the bulk of material (e.g. glass colours)
- The vivid blue colour of natural ultramarine pigment can only be maintained within aqueous solutions and egg tempera which binds the pigment.
- Oil based solutions of ultramarine are less favourable due to a low refractive index leading to a dark colour and a highly viscous consistency rather than the vivid blue when applied on a surface in thick layers
describe paints as consisting of:
- the pigment
- a liquid to carry the pigment
- Paints consist of a binder, a pigment and a medium.
- A binder is also called a resin, it is the glue that holds the paint together.
- Pigments come in two basic varieties - colorant pigments add colour to the paint and extender pigments develop certain characteristics of the paint e.g. gloss.
- The liquid that keeps the pigment and the binder flowing together is the medium. This solvent affects drying time and film thickness.
describe an historical example to illustrate the relationship between the discovery of new mineral deposits and the increasing range of pigments
- Paleolithic cave paintings at Lascaux, France date back to 15,000 B.C. The Paleolithic artists used mineral oxides, either iron or manganese to produce only three colours - red, black or yellow.
- Iron oxide was used by painters from the Middle Ages to the Renaissance. Like cave dwellers these artists including Michelangelo and Rembrandt, used natural chalks containing mineral pigments. The iron oxide pigment was covered with enough clay to give it softness and texture without covering the colour.
- The pigment sienna owes its name to the Italian city Siena, located in Tuscany. The pigment was mined here from the Renaissance until World War II.
- Medieval Italian painters used terra verte for painting shadow flesh tones. Its commonly used synonym, Verona Green comes from terra verte's prevalence in the area of Verona, Italy. This green pigment increased the range of pigments available to artists. It is an iron silicate mixed with clay, producing colours that range from blue-green to yellow-green.
identify data, gather and process information from secondary sources to identify and analyse the composition of an identified range of pigments
- You need to decide on the range of pigments you will investigate for this dot point. A suggested list is given below in the next dot point.
- If you decide not to use these you will have to gather information on other pigments. Look on the Internet and look in encyclopedias or technical books.
- To process the information draw up a table with the name of the pigment in the first column and the chemical formula for the pigment in the second column. See what relationships there are between the composition of the pigment and its properties.
analyse the relationship between the chemical composition of selected pigments and the position of metallic components(s) of each pigment in the Periodic Table
Pigment Composition Metal Naples yellow antimony oxide Sb yellow orpiment arsenic(III) sulfide As malachite copper carbonate Cu azurite copper carbonate Cu haematite iron oxide Fe limonite iron oxide Fe galena lead sulfide Pb cerussite lead carbonate Pb cinnabar mercury sulfide Hg cassiterite tin oxide Sn zincite zinc oxide Zn
- The metallic components of pigments used as a source of colour are predominantly from the transition metal section or d-block of the Periodic Table.
- Titanium, chromium, manganese, iron, copper, zinc and mercury are all transition metals. Tin and lead are in group IV, while antimony and arsenic are in group V.
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