imageColin Berry explains*:

A medieval-provenance TS would never have been commissioned in the first place as a painting (from which pigment has subsequently been shed to leave a ghost image). Why not? Because of an obvious point that I omitted to mention – namely the double image (frontal v dorsal). It was clearly intended to represent a burial shroud, and one might even suggest that it’s the double-image and its appeal to the visual senses as having an up-and-over origin that makes it so iconic, even to modern eyes.

If one goes to the trouble of producing a life-size double image on up-market linen to represent the imprint left by a real person (no matter whom) then one does not employ a paint brush and artists’ pigments. The simplest medieval pilgrim would have spotted straightaway that he was looking at a painting, not a holy relic as billed.

Best explanation I’ve seen so far, at least in blogspace during the last few days. But then again, what does that leave. Thermal Imprinting?  Painting with lemon juice?  Non-brushstroke painting methods?  Photography?  Sun bleaching with glass templates?

There is something nobody has thought of. And maybe that something has nothing to do with faking a double image burial shroud. And since I don’t buy into any of the currently suggested naturally occurring chemical hypotheses or any of the “cosmic ray” image producing suggestions, I feel that we are, for now, nowhere except at a lot of dead ends. My gut still tells me it’s real.

* scroll down to September 26, 2014 at 2:45