The Simple Chemistry of Ancient Egyptian Paint

20th century copy of a painting from the tomb of Anen at Thebes (Theban Tomb 120), 18th dynasty https://www.metmuseum.org/art/collection/search/548566

First presented at SolisticeSchool, 2 August 2023 https://solsticeschool.scholar.social/

Introduction

All over Egypt are walls covered with colourful paintings. Colourful reds, greens, and blues decorate buildings that spent a millennium or two without a roof. Goods from tombs and the walls of tombs are even more colourful. How did the ancient Egyptians create such long-lasting paintings? The answer is a combination of a hot, dry climate and a deliberately simple, stable painting technology.

Overview of Traditional Painting

Most paintings in most parts of the world before the 19th century were made by the same basic technique.

colours and tempers, or pigments and binders

Pigments are ground (dry) or mulled (wet), sorted by particle size (eg. by shaking in water and pouring off) then mixed with binders and applied

Advantages: – easy to transport and store

gives artist control over the properties (thick or thin, stable or removable)

Disadvantages:

more physical labour by the artist
need to heat glue pot and keep gum arabic solution from evapourating
danger of inhaling dry powder

Cakes of red and black ink (gum arabic + pigment) as analogies for modern watercolours (still used in Islamic times although iron gall ink grew in popularity)

Aqueous media (hide glue from boiling down skins and connective tissues or plant gum eg. gum Arabic from the Sahel)
white gesso surfaces (hide glue + chalk or gypsum)
gold leaf surface
chewed-stick, bundle-of-sticks, reed brushes not quills or hair brushes
usually one or two layers of sketching (scratching, charcoal, red paint) followed by the final painting
not much evidence for transparent varnishes to create a watertight, airtight layer but wax was sometimes used to make part of a painting look glossy

Rule Zero for Understanding Ancient Egyptian Art

Our Egyptian art is the art of the pharaohs and the great temples and the people who lived comfortable lives because they were close to the pharaohs and the great temples. We don’t know a lot about how the inside of ordinary houses were decorated because mud brick decays and wood rots or is salvaged. We can see that the official art style changes with political changes, and we see that there were strict conventions about who could have what: for example, images of the gods do not appear in early private tombs, but only temples and to the royal tombs (Robins, Art of Ancient Egypt, p. 138). So when we think about ancient Egyptian art we are thinking about art made by a small community of artists for a small community of patrons with very specific and conservative demands.

Black

carbon based eg. lampblack, charcoal

Very few traditional alternatives (medieval Egyptians sometimes used indigo)

White

calcium carbonate (chalk, whiting, CaCO3)
huntite, or magnesium calcium carbonate (Mg3Ca(CO3)4)

NB. Huntite entered the scientific literature in 1953, but I see claims that it had been used widely as a pigment in eg. Australia, Greece, and the Pacific Northwest, and I wonder if any of its traditional names are known

Calcium carbonate minerals are widely available in the eastern and western deserts

Reds and Yellows

red ochre or hematite Fe2O3
iron oxides or ochres
occasional cinnabar (Mercury sulfide, HgS)

Iron oxides are also widely available in the eastern and western deserts

Blues and Greens

mainly copper based
the most difficult colour to obtain: blue plant dyes are not lightfast and often rather dark in paint, lapis lazuli only available from Badakhshan in Afghanistan (and method to extract the lazurite only developed in middle ages), various forms of corroded copper unpredictable in natural form and fiddly to make.
therefrore before 3000 BCE the Egyptians invented the first artificial pigment. They called it artificial lapis lazuli (ḫsbḏ-ỉrjt,), Greeks and Romans gave it generic names like κύανος kyanos “blue? lapis lazuli?” and caeruleum “sky blue”
Egyptian blue and Egyptian green, calcium copper silicate (CaCuSi4O10 or CaOCuO(SiO2)4)
Vitruvius on architecture: grind sand, copper, and natron, roll into balls, bake in a furnace.
problem: what kind of natron (probably plant ash not the sodium carbonate mineral)
problem: modern analysis shows a calcium carbonate as well as a quartz sand (did they add it separately or just use a sand with both components?)
grinding down the cakes or balls into powder

Colour varies depending on the proportions of the ingredients (more lime > greener); brightness varies with particle size, crystal size, proportion of glass to calcium copper silicate

Egyptian blue remained the dominant blue pigment in the Mediterranean and West Asian world until the Roman empire and its trade networks began to collapse. It gave a deep, stable colour and was not too difficult to make or work with. Pigments were the killer app of early industrial chemistry in the 19th century. As we will see, Egyptians did not favour some of the artificial pigments used by painters in other cultures.

Egyptian bliue is important!

First artificial pigment (pigments were key to invention of industrial chemistry in the 19th century)
Ancestor to glassmaking (remained an Egyptian specialty until the Middle Ages)
First archaeological chemistry to identify its composition (shortly after rediscovery of Pompeii in the 18th century!)

Absent Tempers

Egyptians did not use some tempers which later European painters liked:

egg white
egg yolk (waterproof, fast drying)
seed and nut oils (problem: slow drying)
true fresco (where paint on fresh lime plaster and the pigment bonds with the plaster rather than sitting on top)

Egyptians kept many geese and ducks and eventually chickens. They also hunted birds in the marshes. So they certainly had access to eggs.

Why?

lack of lime plasters for fresco (lime requires kiln requires fuel)
dry environment
expense of using good protein in painting?

Absent Colours

lead-based pigments (lead whte with superior covering power to the calcium whites, red lead which is brighter than ochre)
arsenic sulfides (orpiment, realgar) are rare and mostly late and/or royal (eg. the tombs of New Kingdom pharaohs)
plant-based pigments eg. woad, indigo, lac (pure pigment eg. indigotin, lakes where the colour is precipitated onto a white substrate, Maya blue which embeds the indigotin in clay to protect it from the sun)

They also avoided some pigments which seem consistent with their approach:

purple (iron oxide), brown (iron oxide), and green earths (celadonite and glauconite, available on Cyprus)
sienna and umber (manganese oxides)

Why?

Limited availability? Lack of much dyeplant farming compared to West Asia or Europe, limited contact with the Indian Ocean for dragonsblood and lac and brazilwood, far from Bactria for lapis lazuli. Are there lead mines in Egypt?
Avoid danger of chemical reactions between pigments eg. lead white and verdigris
Avoid toxic materials
Valourization of certain colours and painting techniques (eg. purple not important like in Roman world, creating illusion of depth not important)
Chosen pigments are all lightfast, airfast, waterfast

Although Egyptian painting technology was very simple and conservative, it still created beautiful things which last for thousands of years. Although it was challenged by first the Macedonian conquest and then absentee Roman rule, the Bronze Age Egyptian tradition of art continued until the defunding of the pagan temples after the coming of Christianity.

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