Oh, no, not again... The Shroud of Turin is back in the news
Sunday, March 2, 2008
Keywords: radiocarbon dating, microscopy, microanalysis, pigment, authenticity
Above: The most famous radiocarbon-dated artifact in the world. Credit: Wikipedia.
After last year's "Jesus tomb" documentary and subsequent archaeological controversy, I should have known the Shroud of Turin would soon be back in the news and the subject of a new documentary. Nevertheless I was very surprised to see the shroud appear in the archaeological headlines twice in as many weeks!
Now the shroud fits the definition of an artifact -- according to the American Heritage Dictionary, an artifact is "an object produced or shaped by human craft" -- but there aren't any archaeological questions that the shroud could answer if it was proved to be either two-thousand- or seven-hundred-years-old. This shroud really isn't any more "archaeological" than a single Roman sculpture or medieval tapestry -- take your pick.
Accordingly, I really didn't think I should post the articles here, but they started popping up on other archaeology sites. Here's the reason I changed my mind: the Shroud of Turin is the most famous carbon-dated artifact in the entire world. In the Physics and Archaeology article I posted yesterday, dating the Shroud of Turin is cited as "a celebrated application" of radiocarbon dating, despite not answering any archaeological questions. It is simply a well-known application because the subject is so famous. Everyone has heard of it. It is not an example of how carbon dating refined or changed our knowledge about how people lived in antiquity.
The first article that popped up on my radar was about new radiocarbon tests of the shroud...
Age Test of Shroud of Turin Planned
A British scientist is overseeing new tests on the Shroud of Turin that he says will show it dates to the time of Jesus of Nazareth.
Professor Christopher Ramsey of Oxford wants to check the theory that some type of contamination of the cloth caused the carbon-dating tests run in 1988 to mistakenly peg the shroud as a medieval forgery.
The 14-foot-long cloth bearing the image of a man is said to be the burial shroud of Jesus. However carbon dating 20 years ago indicated the cloth dated from A.D. 1260-1390.
Ramsey's retest is based on the theory that the level of contamination on the cloth required to skew carbon-14 dating results is far less than had been thought back in the 1980s, The Telegraph said Monday.
The project will be covered in a BBC documentary that will reportedly include new supporting archaeological evidence.
"This new theory only requires 2 percent contamination to skew the results by 1,500 years," said David Rolfe, the director of the documentary. . .
I really hope that first sentence is a mischaracterization of what Ramsey truly said, otherwise he seems biased or like he's predicting the future. Three tests by three labs gave dates in the 13th and 14th centuries. The burden of proof right now lies with those who believe the shroud is two-millennia-old. We don't know what the results of any new tests will be, so no one should be saying what the results "will be" ahead of time. To do so makes it look like archaeologists and other scientists make up their minds ahead of time and seek out the "proof" that fits what they expected to find -- we don't want to present the public with such an image of our work.
It sounds, though, that the documentary's director, David Rolfe, is a driving force behind this new test. Rolfe is a shroud "enthusiast" and has made previous documentaries about it. He even tried to make a film in the 1990s in which DNA from the Shroud of Turin was utilized "to clone -- Jurassic Park-style -- the person to whom the blood belonged, whoever it may be." Consider that when estimating the credibility of his "theories" about contaminated samples, erroneous dates, misunderstood behaviors of atmospheric carbon, or whatever.
Then came a story from the Discovery Channel about high-resolution photography of the shroud:
Shroud of Turin Gets High-Def Scrutiny
By Rossella Lorenzi
The Turin shroud, the 14- by 4-foot linen long believed to have been wrapped around Jesus' body after the crucifixion, has entered the digital age.
A huge 12.8 billion-pixel image was made of the linen, on which the smudged outline of the body of a man is indelibly impressed. The image was made following a Vatican request to obtain the most detailed reproduction of the yellowing ancient cloth. The technology allows a level of scrutiny of the linen as never achieved before.
"The Shroud has been photographed in high definition for the first time. We have stitched together 1,600 shots, each the size of a credit card, to create a huge photo which is almost 1,300 times stronger than a picture taken with a 10 million pixel digital camera," Mauro Gavinelli, technical supervisor at HAL9000, a company specializing in art photography, told Discovery News. . .
"It is like looking at the Shroud through a microscope. You can see the threads, the fibers that make these threads, the damage that the shroud has suffered over the years," Gavinelli said.
As hundreds of shots were taken using sophisticated equipment, the process, itself, was recorded by the British Broadcasting Company, which will be airing a program about the project on the Saturday before Easter.
"It was fascinating. Seeing the shroud within a few inches is a unique experience. The image is very visible, it isn't true at all that it is fading," said David Rolfe, director of the BBC documentary. . .
"There is the possibility that new carbon-14 tests today will produce different results. A new hypothesis has been formulated, and it deals with information that wasn't available twenty years ago," Rolfe said.
The new hypothesis, developed by "another contributor to the film," according to a University of Oxford press release, is being tested by Christopher Ramsey, director of the Oxford Radiocarbon Accelerator Unit. The results will be revealed in the documentary. . .
This endeavor is also related to Rolfe's documentary. It is interesting from a conservation standpoint, but I can't match actual microscopic observations of the real thing, so it isn't really useful for research.
The other side of the coin -- and what people usually forget -- is that the composition of the shroud has also been studied. Walter McCrone of the McCrone Research Institute, a non-profit education and research organization in Chicago, and the College of Microscopy has published five peer-reviewed papers on the composition of the Turin shroud. His findings are summarized on the McCrone Research Institute's website:
According to Dr. Walter McCrone and his colleagues, the 3+ by 14+ foot cloth depicting Christ’s crucified body is an inspired painting produced by a Medieval artist just before its first appearance in recorded history in 1356.
The faint sepia image is made up of billions of submicron pigment particles (red ochre and vermilion) in a collagen tempera medium. The pigments red ochre and vermilion with the collagen tempera medium was a common paint composition during the 14th century. . .
Dr. McCrone determined this by polarized light microscopy in 1979. This included careful inspection of thousands of linen fibers from 32 different areas. . . , characterization of the only colored image-forming particles by color, refractive indices, polarized light microscopy, size, shape, and microchemical tests for iron, mercury, and body fluids. The red ochre is present on 20 of both body- and blood-image tapes; the vermilion only on 11 blood-image tapes. Both pigments are absent on the 12 non-image tape fibers. The paint pigments were dispersed in a collagen tempera (produced in medieval times, perhaps, from parchment). It is chemically distinctly different in composition from blood but readily detected and identified microscopically by microchemical staining reactions. Forensic tests for blood were uniformly negative. . .
In 1980, using electron microscopy and x-ray diffraction, McCrone found red ochre (iron oxide, hematite) and vermilion (mercuric sulfide); the electron microprobe analyzer found iron, mercury, and sulfur on a dozen of the blood-image area samples. The results fully confirmed Dr. McCrone’s results and further proved the image was painted twice – once with red ochre, followed by vermilion to enhance the blood-image areas.
In 1987, carbon dating at three prestigious laboratories agreed well with his date: 1355 by microscopy and 1325 by C-14 dating. The suggestion that the 1532 Chambery fire changed the date of the cloth is ludicrous. Samples for C-dating are routinely and completely burned to CO2 as part of a well-tested purification procedure. The suggestions that modern biological contaminants were sufficient to modernize the date are also ridiculous. A weight of 20th century carbon equaling nearly two times the weight of the Shroud carbon itself would be required to change a 1st century date to the 14th century. . . Besides this, the linen cloth samples were very carefully cleaned before analysis at each of the C-dating laboratories. . .
The shroud's image is comprised of two common pigments in antiquity: ochre and vermillion. Do those pigments sound familiar? Well, I've posted about ochre here and here and about vermillion (also known as cinnabar) here. Unlike the Mali sculptures discussed here, no evidence of blood was found on the shroud.
So where does that leave us? The well-established techniques we use in archaeological science suggest that the Shroud of Turin dates to the 13th or 14th century and was painted in ochre and vermillion. The shroud, though, is not an object of archaeological interest because there are no archaeological questions that it may answer -- it isn't any more archaeologically important than, say, the Mona Lisa or Michelangelo's David.
With a new documentary on its way, though, we're in for a lot more stories like these...
Blog Author: Ellery Frahm