VAPOR MEDIATED ... Paul Vignon in the early years of the 20th century speculated that the shroud image may have been caused by staining vapors traveling between the body and the cloth. He was the first researcher to note that the image seemed to be darker where the cloth and body were closer together. This was later dramatically confirmed by Jumper and Jackson using the VP-8 analyzer. The vaporograph theory has some serious problems, especially with the fact of gas diffusion, but the hypothesis is still in play in various forms.