Dating the Turin Shroud

Comparison of positive (left)
and negative (right) photos

The Shroud of Turin (or Sindone, from the Greek σινδών, shroud) is traditionally thought to be the shroud that covered the body of Christ during the three days that he was buried between his death on the cross and his resurrection. The documented part of its history begins in 1357, when it was exhibited for the first time in Lirey (France). In 1453 it was sold to the Duke of Savoy. In 1532 it was damaged in a fire, and in 1578 was transferred to Turin, where it is located today. Although the Catholic Church allows its veneration, it has never pronounced either in favor or against the authenticity of the Shroud, which from the beginning was the subject of controversy, as some claimed it was a contemporary painting, while others considered it authentic.

In 1898 the Shroud was photographed for the first time and the image was found to be much sharper on negatives than on positives, so the original image appears to be roughly equivalent to a photographic negative.

The assumption that the Shroud is a painting made in the 13th-14th century must deal with the following inklings:

• Why take the trouble to paint a barely visible image, which cannot be seen clearly unless you stand a few meters away?
• Is it believable that someone painted a photographic negative more than half a millennium before the invention of photography?
• The image, seen through a VP8 camera, used by NASA to obtain three-dimensional images on the moon, appears as a three-dimensional image, which is unusual when that camera is used with paintings or photographs.
• The image doesn't show signs of paint, but is made up of cellulose fibers denaturalized by some radiation.
• In the image, the wounds of the nails go through the wrists, which is where the Romans nailed them, but in the Middle Ages it was believed that these wounds would be in the center of the hands, and this is how they appear in all pictorial representations, except on the Shroud.
• Dust from aragonite travertine limestone has been found in the area of ​​the feet, with the same mineral footprint (the same composition of trace elements) as the earth in Jerusalem.
• The Swiss criminologist Max Frei found in the Shroud pollen grains of 58 different species, of which 45 came from the Jerusalem area. In the part of the image corresponding to the head (and only there) were detected pollen grains from Gundelia tournefortii, a thorny shrub that could have been used to make the crown of thorns. Subsequent studies have cast doubt on whether it is possible to detect the biological species (beyond the genus) to which these pollen grains belong. Frei has also been accused of manipulating the data on the pollen extracted from the Shroud.

3D image from the Shroud
(see here)

Against these and other inklings, the carbon-14 dating of a sample cut from the lower edge of the Shroud, performed in 1989 by three laboratories (Arizona, Zurich and Oxford), resulted in a date of origin for the Shroud, with 95% confidence, between 1262 and 1312, or between 1353 and 1384 (see this article). As dates after 1357 must be excluded for historical reasons, the most probable dates for the manufacture of the Shroud would be between 1262 and 1312, or between 1353 and 1357, just before its first documented public exhibition.

In fact, the three labs didn't come up with consistent dates: the Oxford result is the oldest, followed by Zurich, and finally Arizona. In fact, the results for Arizona and Oxford hardly overlap, taking into account the confidence interval. The situation was quite different when they computed, as a control experiment, the dates of three other artifacts, where the results of the three laboratories were much more consistent.

Various criticisms have been raised against the accuracy of the carbon-14 tests:

• The part from which the sample was taken could have been repaired in the 16th century, when it is known that other areas damaged by the fire were repaired, so that the analyzed material would not be completely made of the original material, but would include much more modern fibers, so carbon-14 dating would have given an intermediate result. This would also explain the differences observed between the three laboratories, as the proportion of new material could have been different in the analyzed samples.
• The area where the sample was cut in the place where the Shroud was usually held when it was shown to the public, so there could have been contamination by bacteria, which would have formed a bioplastic coating of modern origin on the fibers of the sample, giving rise to incorrect dating.
• Other forms of contamination could come from smoke from the fire to which the Shroud was subjected, or from a deposition of airborne carbon particles.

The Turin Shroud is the most studied artifact in human history. As a summary of all these studies, Phillip Ball, former editor of Nature, wrote this in 2019 in an article published in the Chemistry World journal:

Nothing published so far on the shroud, including this paper, offers compelling reason to think that the 1989 study was substantially wrong – but apparently it was not definitive either.

The same post in Spanish

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Manuel Alfonseca