The image is extremely faint and difficult to see. Much more detail can be seen in contrast-enhanced and ultraviolet photographs; however, they are somewhat misleading to studies on image formation. Whatever produced the image color did not produce very much color. Scientific observations were planned in order to learn as much as possible about the image distribution and chemical composition.
The Shroud was observed by microscopy, visible and ultraviolet spectrometry, infrared spectrometry, x-ray fluorescence spectrometry, and thermography. Later observations were made by microchemistry, petrographic microscopy, scanning-electron microscopy, energydispersive x-ray analysis, pyrolysis-mass-spectrometry, and laser-microprobe Raman analyses.
Without making any assumptions that are based on the appearance of the image, some statements of fact can be proved from the scientific observations:
= Reflectance spectra, chemical tests, laser-microprobe Raman spectra, pyrolysis mass spectrometry, and x-ray fluorescence all show that the image is not painted with any of the expected, historically-documented pigments and media.
= No painting pigments or media scorched in image areas or were rendered water soluble at the time of the AD 1532 fire.
= Direct microscopy showed that the image color resides only on the topmost fibers at the highest parts of the weave.
= The color density of any specific image area depends on the batch of yarn that was used in its weave. The cloth shows bands of slightly different colors of yarn.
= Adhesive-tape samples show that the image is a result of concentrations of yellow/brown fibers.
= The image does not fluoresce under ultraviolet illumination.
= The image of the dorsal side of the body shows the same color density and distribution as the ventral, and it does not penetrate the cloth any more deeply than the image of the ventral side of the body.
= Thermography proved that the emittance of the image was the same in all areas. The entire image formed by the same mechanism. Spectra and photography confirmed this observation.
= The only image color easily visible on the back side of the cloth is in the region of the hair. Fanti and Maggiolo were able to show traces of face and hand images by image processing.
= No image formed under the blood stains.
= The image-formation mechanism did not damage, denature, or char the blood. The blood can be removed with a proteolytic enzyme. The blood produced hydroxyproline at low temperatures in the pyrolysis/ms spectra. It was never heated significantly. Image formation had to be a low-temperature process.
= Image color can be chemically reduced with diimide, leaving colorless cellulose fibers. All image color resides on the outer surfaces of the fibers.
= The medullas of colored image fibers are not colored: The cellulose was not involved in color production.
= The color of image fibers was often stripped off of their surfaces, leaving molds of the fibers in the adhesive. Growth nodes can be seen in the molds. The colored layers show all of the same chemical properties observed on intact image fibers (see 12 above). All of the color is on the surfaces of the fibers. The colored layer is 200-600 nanometers thick.
= Chemical tests showed that there is no protein painting medium or protein-containing coating in image areas. The image was not painted with glair, and it follows that microbiological activity did not produce the image.
= Microchemical tests with iodine detected the presence of starch impurities on the surfaces of linen fibers from the Shroud. An impurity layer could be seen by phase-contrast microscopy.
= There is no evidence for tissue breakdown (formation of liquid decomposition products of a body). Body fluids (other than blood) did not percolate into the cloth.
= Any radiation that is energetic enough or sufficiently intense to heat the cloth enough to cause the initial dehydration reactions of cellulose would penetrate into a fiber to a distance determined by its energy. Simple heating would change both the cellulose and blood. Both protons and neutrons leave characteristic tracks in flax fibers. The image fibers could not have been colored by energetic radiation.
= Rapid heating, as when linen is scorched with a torch, leaves characteristic, small balls of solidified melt at the ends of fibers. No such features can be observed on the Shroud.
= The cloth does not show any phosphorescence.
= The blood on the cloth is still largely red. Old blood is normally black. Blood that has been hemolyzed remains red for a long time.
= Neither aloes or myrrh could be detected on the cloth.