It's not a scorch. A scorch in linen would fluoresce. The image does not fluoresce. . . yet the scorches from the fire of 1532 do fluoresce. However, we know what it is made of. It's a sugar like caramel coating caused by a meloidin reaction in the starch of the soapwort that was left over from washing and starching the hanks of linen yarn before it was woven into cloth when it was "fullered." It exists only as a surface phenomenon in that coating that is thinner than a soap bubble and about as fragile.
The image is strangely vertically collimated. There is no evidence that image formed horizontally or even by a force at an angle even slightly away from the vertical both up and down. Whatever the force was, it attenuated by about ten centimeters distance from the body. . . or at least to the point of inefficacy in forming the meloidin change in the soapwort.
But it was caused by some kind of radiation, right? That's what I meant by "scorch."
What does "vertically collimated" mean? That the rays of radiation were parallel?