Our research to further understand the Book of the Dead of the Goldworker Amun, Sobekmose continues. Carbon-14 (C-14) dating was one of the first scientific analytical techniques that we employed to confirm the date for this piece, thought to be approximately 1420 B.C.E. based on previous research.
Detail from the Book of the Dead of the Goldworker Amun, Sobekmose. New Kingdom, Dynasty 18, ca. 1479-1400 B.C.E. Ink and pigment on papyrus. Brooklyn Museum, Charles Edwin Wilbour Fund, 37.1777E.
For several reasons, it is a rare opportunity for us to test Museum objects using this technique. One necessary condition is that the object must fit into a certain time range. C-14 dating requires that the material in question be at least 2,000 years old (and up to 50,000 years old) to get a result with a significant certainty. Fortunately, we believed our papyrus fit into this time range.
Additionally, with works of art on paper, we do not often have an expendable sample for this type of analysis. Unlike the Fourier-Transform Infrared Spectroscopy and X-ray Fluorescence Spectroscopy described in the two previous posts which require no sample and were used to investigate pigments and adhesives used on the papyrus, C-14 dating requires a sample from the object, usually about 5 mg, which is destroyed during testing. After placing as many loose fragments as best as possible (we will talk more about our repairs in a future post), we had some very small ones remaining with no ink or coloring which were unplaceable. We consulted with our curators and decided that we could use a few of these small fragments for C-14 analysis.
Fragments circled are approximately 5 mg of sample.
There are only a handful of labs in this country that do this kind of analysis. We sent our sample to the Accelerator Mass Spectrometry (AMS) laboratory in the Physics Department at the University of Arizona in Tucson for analysis. C-14 dating was developed after World War II in the 1940s and 1950s and the principal is based on the measurement of the unstable carbon isotope 14C levels in a sample as compared to modern, known standards of the stable carbon isotopes 12C and 13C, which comprise the great majority of atmospheric carbon. (Isotopes are different forms of the same element.) The 14C atoms are produced when cosmic rays bombard the Earth’s upper atmosphere and produce nuclear reactions which produce neutrons. (About 2 atoms per second per centimeter squared are produced.) These neutrons react with nitrogen atoms to form 14C atoms, an unstable form of carbon. 14C mixes up into the atmosphere and is taken in by plants during photosynthesis, and other organisms as part of the food chain.
The 14C in an organism is always being replenished from the atmosphere at a constant rate while it is alive, and the ratio between it and the stable carbon isotopes is approximately constant with time. But when a plant or organism dies, its 14C intake stops and what remains will decay at a known rate (half life of 5,730 years). Therefore by measuring the amounts of the 14C and comparing it to known 12C data, an approximate age can be determined.
Spectra of C-14 results from University of Arizona AMS laboratory.
Our results are given in the spectra above. With some interpretation this shows that the results we received from the C- 14 method of scientific analysis are indeed consistent with our current understanding of our Book of the Dead, i.e. that it was produced in the New Kingdom, Dynasty 18, c. 1420 B.C.E.
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This post is part of a series by Conservators and Curators on papyrus and in particular the Book of the Dead of the Goldworker of Amun, Sebekmose, a 24 foot long papyrus in the Brooklyn Museum’s collection. This unique papyrus currently in 8 large sections has never been exhibited due to condition. Thanks to a generous grant from the Leon Levy Foundation, the entire papyrus is now undergoing conservation treatment. The conservation work is expected to last until fall 2011 when all 8 sections will be exhibited together for the first time in the Mummy Chamber. As each section is conserved, it will join those already on exhibition until eventually the public will see the Book of the Dead in its entirety.
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Eastern Parkway/Brooklyn Museum
Hi,
1. Why do you claim that “the material in question be at least 2,000 years old”?
2. Why do you use an outdated version of OxCal and calibration curve? The latest versions are :
OxCal V 4.1.7 Bronk Ramsey 2010. r5; atmospheric data from Reimer et al (2009). This does not alter the conclusions significantly, but using the latest cal curve is good form.
regards
Ray
It’s hard to accept at face value the assertion that C14 dating validates the previous estimate of 1420 BCE, given that calBC 1420 falls outside the range of the 2 sigma bracket for this date, which implies that the correct age falls somewhere between calBC 1620 and calBC 1430 with a 95.4% probability. The probability that the date is calBC 1420 therefore falls in a zone of probability less than 5%. The intercept of this calibration curve places the most likely estimate of its age around 1500-1510 BC, as the zone of highest probability within the one-sigma curve (calBC 1540-1450) also implies. All still suggests 18th Dynasty, but in the interest of educating the public about the proper use of techniques like C14 dating, it would be appropriate for a museum to acknowledge that their dating results actually complicate the curator’s prior expectations and require further examination of their preconceptions, rather than suggesting fallaciously that the results confirm their earlier hypotheses when the data presented clearly do not.
Dear Mr. Kidd,
Thank you for your response to our blog on C-14 dating of papyrus and for pointing out that a material does not have to be 2,000 years old to be eligible for this testing; I misread this somewhere and appreciate you catching that. As far as the use of calibration curves, I refer you to our testing facility at the University of Arizona, http://www.physics.arizona.edu/as. They should be able to tell you why they used what they did. We did not run the test ourselves. Many thanks again for your comment.
Dear Kevin,
Thank you for your comments on our blog on C-14 dating of papyrus. To answer your question, according to our curators, precise dating within the field of Egyptology is rarely attainable, and indeed, an exact date of 1420 B.C.E. would not be perfect according to our spectra or knowledge, which is why the date of 1420 B.C.E. is given as approximate. Our curators believe this to be a fairly accurate date, but more broadly, they believe our papyrus dates from the early to mid-18th Dynasty. Adding to the confusion unfortunately is that the interpretation of radiocarbon dating is subject to many complex problems. That date, whether it’s c. 1420 B.C.E. or c. 1430 B.C.E or earlier, is based on a combination of the scientific and historic information we have at hand. Thank you very much for your comment.
Dear Mrs Danzig,
I have been for years responsible in the Book of the Dead project in Bonn and have worked in my PhE thesis about the dating of BD (Untersuchungen zu den Totenbuch-Papyri der 18. Dynastie, London/New York 1987). By then I had never seen the manuscript of Sebekmose. Now looking at the script and the bit of the vignette it is clear for me, that the manuscript is of a earlier date than you have presumed. 1420 BC would be in the time of Amenhotep II, which is according to the hieratic script and the direction of the text impossible. Maybe you could send me some other images of the papyrus. This would enable me to give more detailed criteria for its dating.
Best wishes
Irmtraut Munro