[RS]

"Interestingly enough the images can be removed from the fibers with adhesive and dissolved with reducing agents."

Is this normal that "in some areas it has turned straw-yellow due to a chemical change which is not unlike caramelization (browning of sugar by heat) or Maillard (chemical reaction of sugar with amines or proteins)" causes enough physical change in the property of the outer layer that it can be selectivly removed by the application of a piece of tape ?

I appreciate the fact that you do not presume to have the answer, not like the "1/10 second burst of energy " supporters.

[shroudie]

RS, I wasn’t clear. Good catch. Actually, the outer layer, the coating, can be removed with adhesive (significant pressure) or reducing agents, such as diimide, whether or not it was chemically altered. When STURP examined the Shroud in 1978 several sticky tapes were applied to collect particulate matter. Those tapes are still being examined as there are thousands of particles. Some of those particles were whole fiber lengths, some with image and some without image. Some particles were flecks of the coating, some yellowed and some not yellowed. You could say that some of the image, though not noticeably so, was inadvertently destroyed. In the lab, the coating has also been removed and sometimes it remains on the tape when fibers are lifted from the tape.

Where the image has been formed by a chemical change, the coating is thinner by a few nanometers (only relative microscopic comparisons are made) and crackled. The reason is that the chemical change is dehydrative. And because it is less bonded because of the change, the layer will pull away more easily. Ray Rogers, a Fellow of the University of California, Los Alamos National Laboratory, a chemist who has scientifically examined the Shroud—in Turin—and studied the object for more than 27 years, summarizes nicely:

“There is absolutely no doubt that the image color exists in a thin layer on the surface of image fibers. The layer is amorphous, and it seems to have an index of refraction relatively close to that of the linen fiber. The layer is quite brittle, and many flakes of the color have flaked off of the fibers. Colorless cellulose can be seen where image color has flaked off. The flakes can be seen and identified on the adhesive of sampling tapes. The flakes have the chemical properties of the intact image color on the fibers. Non-image areas show an impurity coating on the surfaces of the linen fibers. It is slightly thicker than the colored image layer, as would be expected. When a material is dehydrated it shrinks. When the impurity layer reacted to produce the color, it got thinner.”

It should be pointed out that these layers, visible with phase-contrast microscopy, are extremely thin. On the Shroud they have been observed to be approximately 180 to 600 nanometers thick. This is in the range of the wavelengths of visible lights.

Shroudie