Earlier this morning, the classical galleries were closed for ‘research and conservation.’ Bill, our chief conservator, and I were there to take samples of the bright pink pigment found on the South Italian ceramics. We have a good idea of what this pigment might be but we’ll send samples to a colleague in Italy for scientific confirmation.
Sampling is always a delicate procedure because it is destructive. Bill had to scrape some of that fabulous pink off the four vessels that use it in their decoration. We picked locations on the vessels that are less visible when you’re visiting the galleries and viewing the pots. You shouldn’t notice where the pink pigment was scraped off.
The results will be published in the NCMA’s upcoming catalogue of classical art.
Just before the holidays, Mark the marble guy dropped by the NCMA to take one last look at the classical marble sculptures before he could hand over his reports and catalogue entries. Again we had to work in the dark galleries of the museum, but luckily we didn’t have to start as late as before… the sun sets much sooner in winter!
Assisted by Caroline “the Younger” (who was my intern in the spring), we reexamined the troublesome Hercules and just a few other sculptures with Mark’s nifty and very powerful flashlight, his new portable microscope and under ultraviolet lights. We also took photographs (UV and VIL/IRR) of details based on our earlier “night at the museum” sessions. This should be the last examination of the marbles and the research on these works of art is pretty much completed… but the project continues with the study of other ancient objects from different Classical cultures and made from different materials.
The research on the NCMA’s classical collection continues and that is making me really, really happy. It might not be related to ancient Egypt or Nubia, but at least it’s ancient! Very late in November, our intellectual travels took us to South Italy and Sicily, where the ancient Greeks established colonies. Keely H, who is an expert on this material, took a look at the small collection from the art historical and archaeological standpoint; she was assisted by yours truly as well as Stacey, NCMA conservation technician. Objects conservator Corey was examining the collection from the conservation perspective.
The collection consists of various ceramic vessels, some of which are wonderfully coloured… but are all these pigments actually ancient? That is the question! We are trying to find the answer by looking at the objects under UV lights, by X-ray fluorescence (which was done by NCMA paintings conservator Noelle who is not on the photos), and hopefully even by sampling for further testing in later months. Stay tuned for that!
An interesting article (especially the last two paragraphs) about new uses of Egyptian blue, with which you should now be familiar if you’ve read some of my posts during the summer of 2014. It’s not often that art comes to the aid of science; it’s usually the other way round. It was appeared in Chemistry World and Paul Brack won the 2014–15 Chemistry World science communication competition with this article.
Today, I’m combining two chronicles—Did You Know? and ARCHAEO-Crush—using one group of artefacts: the Chinese Terracotta Army of Emperor Qin Shi Huang.
Did you know that on this day back in 1974 two local farmers in Xi’an came upon this incredible discovery while digging a well? Archaeologists soon arrived to investigate and the rest is history…
Emperor Qin Shi Huang’s terracotta army, intended to protect him in the Afterlife. (Photo taken by my Dad during his trip to Xi’an.)
CHINESE TERRACOTTA ARMY Type: artefact (funerary statuary) Civilisation: ancient China Date: 210–209 BCE ARCHAEO-Crush: I love those terracotta warriors and other figures. There are so many of them (more than 8000 soldiers, horses, chariots and non-military figures) and remarkably each one has individual features. There aren’t two alike! What I find utterly fascinating (and horrifying) is that the statues were fully painted, but in just a few minutes the pigments dry up and flake away with exposure to the dry air at the time of excavation. After much research, scientists and conservators have been able to consolidate the pigments with polyethylene glycol 200 (PEG200) and electron beam polymerization. I find conservation absolutely fascinating… You may have hear of PEG before as it is also used in the consolidation of water-logged wooden artefacts like Viking ships. Bucket list status: I have seen a selection of soldiers, chariots and horses in The First Emperor: China’sTerracotta Army, an exhibition held at the High Museum in Atlanta in 2008-09. I would definitely like to see them again, this time in China. It’s at the top of my bucket list! Additional info: UNESCO World Heritage 441
The science geeks interested in learning more about the conservation aspect can read the Getty’s 2010 Conservation of Ancient Sites along the Silk Road(PDF available online, at the virtual library on their website), which features a scientific article (pages 35-39) on the consolidation of the colour pigments of the terracotta army.
Now that we know there are traces of pigments on some of the Classical sculptures, it is time to take samples of all colours found on these objects. This task falls to Mark, who has to take minuscule samples of the pigments using the microscope or a head loupe to see them. Sampling will enable us to conduct further experiments (or have them conducted by a lab) to confirm the nature of the pigments with other scientific methods.
With the microscope, Mark locates Egyptian blue grains to sample.
Mark takes a sample of Egyptian blue from the head of Aeschylus.
Here is a minuscule sample of Egyptian blue (I believe it is magnified 200 times).
Wearing a head loupe, Mark takes a sample (pink, I think) from the chlamys (cloak) of the Celestial God.
The microscope is installed to examine the area between the husband (left) and the wife (right) on the Funerary Monument.
Mark takes a look at the area next to the head of the wife on the Funerary Monument.
Mark takes a sample from the sarcophagus fragment.
After having identified the sculptures that still bore traces of pigments, the next step was to do x-ray fluorescence. This is a non-invasive technique used for the identification of non-organic pigments. It is not enough to note the presence of pigments on sculpture and take photographs of their location; we need to know of what these mineral pigments are made. This helps with the dating and authentication of the work of art because certain pigments are used in specific countries (or cultures) or during specific historical periods.
The analysis was conducted by Scott Pike, associate professor of geology and earth sciences at Willamette University, who had in his luggage his very handy x-ray gun. While we worked together, Scott explained how this Star Trek phaser looking thing works. This instrument send x-rays on the non-organic matter we wish to analyze. This results in electrons being bumped from their atomic orbital positions, releasing a burst of energy (fluorescence) that is characteristic of specific elements (elements of the periodic table, that is). The fluorescence is identified and recorded by the device. Each pigment will have its own combination of elements. Thanks to this technique, we can tell if the red pigment is actually red ochre (an iron oxide used in ancient Egypt) or cinnabar (mercury sulphide used by the Romans).
The x-ray gun is controlled with a computer. Although I did have my photo taken with very cool looking instrument (I just had to!), I assisted Scott by manning the computer while he held the portable XRF device to do the analysis. Elizabeth joined us in the galleries for a while and that allowed me to take a few pictures. Luckily, x-ray fluorescence does not require to be done in the dark. So we didn’t have to work late nights at the museum. All we had to do was stanchion off a work area around the sculpture under examination so that people did not disturb us… but we did have some people intrigued enough to stop by and observe what we were doing.
Acne treatment for our Celestial god? Not really. We have to take a reading from a neutral zone as well as the places where pigments are found.
The ram on the sarcophagus fragment is being poked in the eye by Elizabteth. The location of each analysis is identified on a picture. We just point with a stick.
Scott applies the x-ray gun to the eye of the ram, which has some traces of red pigment.
Scott and Elizabeth take readings on the sarcophagus fragment.
Computer monitor showing the spike chart during analysis.
The Cypriot Priest not getting laser eye surgery… the red pigment used to colour his eyes is being analyzed by the portable XRF device.