It’s not a picture, but a sign, leaved by a body.The scientific reasearch could state the character of the Holy Shroud, but could not solve the mistery of its origin. That’s why the research carries on.
It was with the first photograph taken in 1898 that the totally new and fascinating period of the “scientific history” about the Holy Shroud has started. The question pertaining to the modality of the formation of the image was one of the first research themes which gave origin to a deep study by different scholars, right at the start of the 20th century. They wished to understand by which natural process a corpse would leave traces on a linen cloth characteristic of those visible on the Shroud.
Numerous theories were proposed in this period spanning over a hundred years. Many of them were also experimental attempts to reproduce (starting from a corpse or through an artificial method) a similar image to that of the Shroud. Someone thought that the imprint was caused by chemical reactions between the ammoniac evaporations emitted by the corpse and the aloe and myrrh (natural fragrant substances used in ancient times to honor the corpses) present in the linen; some others have thought that it could be radiation from the body or from some external source to the body. Some others have tried experiments using thermal energy generated from a statue of heated metal; others have also tried using red ochre to paint an image on a sheet of cloth, etc. In none of these cases were the experimental results really satisfactory (that is, being able to realize a similar image as that of the Shroud) and some of the characteristics of the image of the Shroud seem impossible to be produced to this day.
The results obtained, however, affirm with certitude that the image was produced through a natural process from the corpse of a human being, and exclude that it be due to the work of some artist through the use of a reproduction technique. In fact, the American scientists of the research group named STURP (Shroud of Turin Re-search Project) who in 1979 made direct experiments on the Shroud, confirmed through a complex series of tests, the absence of pigments and colors on the Shroud, proving, moreover, that the bodily image is absent below the blood stains (and therefore formed on it later) , which is merely some hundredths of a millimeter thick on the cloth’s surface and is “the result of cellulose decomposition, the oxidation-dehydration of the cloth’s surface” which took place through some unknown process and certainly not due to the use of artificial means.
The red stains visible on the Shroud were always considered to be blood stains. But absolute certainty required a detailed examination of the material found on these stains. In 1978 some samples of this material were taken by two groups of scholars (Italian and American) and the tests performed by them in the following years have confirmed it to be human blood of type AB.