A chemical ghost on linen fibers
The image on the Shroud of Turin is not a painting or a stain. Microscopic examination reveals no pigments, dyes, or brushstrokes. Instead, the image exists as a chemically altered layer on the topmost linen microfibrils. This discolored layer is extraordinarily thin, measuring less than 0.2 micrometers (200 nanometers), which is about 2% of the fiber's radius. The image is the result of a chemical change—specifically, the oxidation and dehydration of the polysaccharide structure of the linen itself. This process formed a series of conjugated carbonyl groups, a chemical structure similar to a scorch, but one that lacks the fluorescence typical of a high-temperature burn.
In 1978, the Shroud of Turin Research Project (STURP) conducted 120 hours of non-destructive testing on the cloth. The team of scientists concluded that no known artistic or scientific method from the medieval period could account for the image's unique characteristics. One of the most unusual properties is the three-dimensional information encoded in the image's shading. When processed with a VP-8 Image Analyzer, a device developed for NASA, the varying light intensity of the image translated directly into a topographically accurate 3D relief of a human body. Photographs and paintings uniformly fail this test, producing distorted results.
Conflicting molecular stories
In 1988, three independent laboratories at the University of Oxford, the University of Arizona, and the Swiss Federal Institute of Technology in Zurich performed radiocarbon dating on a sample from the Shroud's edge. The results provided a calibrated date range of 1260–1390 AD with 95% confidence. This medieval dating is a central point of the ongoing scientific debate, as other evidence presents a more complex picture. Statistical analyses of the raw data from the 1988 tests have suggested the samples were not homogeneous, potentially affecting the result.
Forensic analysis of stains on the cloth confirmed the presence of real human blood. Multiple tests identified hemoglobin, serum albumin, and immunoglobulin. The blood is type AB. Unusually, the bloodstains are reddish rather than the dark brown typical of ancient blood. One hypothesis attributes this to high concentrations of bilirubin, a substance produced in the body in response to extreme trauma.
Analysis of dust particles taken from the cloth by Swiss criminologist Max Frei revealed pollen from numerous plant species. While some pollens are native to Europe, many are from plants specific to the Near East, including species characteristic of the Judean desert and the area around Jerusalem.