This January 2018 video says about itself:
The world’s first artificial pigment, Egyptian blue, may help scientists prevent forgery and even save lives.
Discovered: Unknown yellow colors from antiquity
October 15, 2019
Summary: Antique artefacts have been studied by chemists, revealing a hitherto unknown use of yellow in Ancient Egypt
Archaeologists have long known that artefacts from the Antiquity were far more colorful than one would think when looking at the bright white statues and temples, left behind for today.
The statues and buildings only appear white today because the colors have degraded over time. Initially, lots of colors were in use.
This was also true for King Apries I‘s palace in Ancient Egypt. This palace was situated in the Nile Delta, and from here King Apries ruled from 589 to approx. 568 BC.
Fragments of the palace are today kept at the Glyptoteket Museum in Copenhagen, and recently they have been the focus of a collaboration between archaeologists from Glyptoteket, the British Museum, the University of Pisa and a chemist from the University of Southern Denmark.
“We are interested in learning more about the use of pigments, binders and the techniques associated with using them in the Antuquity. It has an obvious relevance for art historians, but it can also tell us about how different cultures in the Mediterranean and the Near East exchanged materials and knowledge and thus connected,” says Cecilie Brøns, classical archaeologist at Glyptoteket.
With this in mind, the archaeologists have worked with professor of archaeometry Kaare Lund Rasmussen from the University of Southern Denmark.
Professor Rasmussen is an expert in conducting advanced chemical analyzes of archaeological objects. Among other things, he has examined the beard of renaissance astronomer Tycho Brahe, Italian monk skeletons, medieval syphilis-infested bones, sacred relics and the Dead Sea Scrolls.
For this project he has taken samples of the palace fragments to learn more about the pigments and binders used.
“We have discovered no less than two pigments whose use in Antiquity has hitherto been completely unknown,” says Kaare Lund Rasmussen.
These are lead-antimonate yellow and lead-tin yellow. Both are naturally occurring mineral pigments.
“We do not know whether the two pigments were commonly available or rare. Future chemical studies of other antiquity artefacts may shed more light,” he says.
Lead-antimonate yellow and lead-tin yellow have so far only been found in paintings dating to the Middle Ages or younger than that. The oldest known use of lead-tin yellow is in European paintings from ca. 1300 AD. The oldest known use of lead-antimonate yellow is from the beginning of the 16th century AD.
Analyzing binders is more difficult than analyzing pigments. Pigments are inorganic and do not deteriorate as easily as most binders which are organic and therefore deteriorate faster.
Nevertheless, Kaare Lund Rasmussen’s Italian colleagues from Professor Maria Perla Colombini’s research group at the University of Pisa managed to find traces of two binders, namely rubber and animal glue.
The rubber is probably tapped from an acacia tree and served as a solvent for powdered pigment. Rubber was widely used as a binder, and it has also been found on stone columns in the Karnak Temple and murals in Queen Nefertite‘s tomb.
Animal glue was also commonly available. It was made by boiling animal parts, in particular the hides and bones, in water to a gel-like mass which could be dried and pulverized. When needed, the powder was stirred with warm water and ready to use.
The researchers also found these color pigments:
- Calcite (white).
- Gypsum (white).
- Egyptian Blue (a synthetic pigment, invented in the 3rd millennium BC)
- Atacamite (green).
- Hematite (red).
- Orpiment (golden yellow).
20 ancient coffins discovered in Luxor, Egypt: here.
This 9 October 2019 video says about itself:
Sites mentioned in the interview:
Bruniquel Cave, France
Fumane Cave, Italy
This video is about the Bruniquel cave.
This 2014 video from the USA says about itself:
Portrait of Isabella de’ Medici, c. 1570-1574
oil on canvas (transferred from panel)
Gift of Mrs. Paul B. Ernst
Filmed in conjunction with the exhibition “Faked, Forgotten, Found: Five Renaissance Paintings Investigated.”
From the American Chemical Society in the USA:
Why some greens turn brown in historical paintings
October 2, 2019
Enticed by the brilliant green hues of copper acetate and copper resinate, some painters in the Renaissance period incorporated these pigments into their masterpieces. However, by the 18th century, most artists had abandoned the colors because of their tendency to darken with time. Now, researchers reporting in ACS’ journal Inorganic Chemistry have uncovered the chemistry behind the copper pigments’ color change.
Copper acetate (also known as verdigris) and copper resinate were used in European easel paintings between the 15th and 17th centuries. Artists typically mixed these pigments with linseed oil to make paint. Until now, scientists didn’t know why the green paints often turned brown with time, although they had some clues. Light exposure was thought to play a role because areas of paintings protected by frames remained green. Also, oxygen appeared to contribute to the darkening process, with the brown color spreading from cracks in the paint that exposed the underlying copper pigments to air. So Didier Gourier and colleagues wanted to analyze the chemical changes that occur in the paints upon light exposure.
The team determined that the molecular structures of copper acetate and copper resinate were quite similar: Both had two copper atoms bridged by four carboxylate groups, but there was more space between resinate than acetate molecules. The researchers mixed the pigments with linseed oil and spread them in a thin layer. They then exposed the paint films to 16 hours of 320-mW LED light, which corresponded to hundreds of years of museum light. This illumination caused bridging molecules between the pair of copper atoms to be lost, which were then replaced by an oxygen molecule, creating bimetallic copper molecules responsible for the brown color. This process occurred more readily for copper resinate than for copper acetate. Boiling the linseed oil before mixing, which some artists did to improve the drying process, slowed the darkening reaction.