Enea, the National Agency for New Technologies, Energy and Sustainable Economic Development, has published a report on five years of experiments conducted in the ENEA center of Frascati on the “shroud-like coloring of linen fabrics by far ultraviolet radiation”. (…) The report notes: “The double image (front and back) of a scourged and crucified man, barely visible on the linen cloth of the Shroud of Turin has many physical and chemical characteristics that are so particular that the staining which is identical in all its facets, would be impossible to obtain today in a laboratory, as discussed in numerous articles listed in the references. This inability to repeat (and therefore falsify) the image on the Shroud makes it impossible to formulate a reliable hypothesis on how the impression was made.

http://vaticaninsider.lastampa.it/en/homepage/inquiries-and-interviews/detail/articolo/sacra-sindone-holy-shroud-sabana-santa-10738/