Postscript promoted, my own, from immediately preceding post:
From Daniel R. Porter on his shroudstory.com site (as it now calls itself):
“I guess you can do that if you ignore or alter facts. However, the Drs. Jackson, Rogers, Di Lazzaro and Heimburger, all independently at different times, have adequately shown that such a theory, hypothesis, wild-ass-guess is wrong by pointing out that heat cannot form a physically superficial discoloration of linen fibers.”
Think what you like about hypothesis v theory, Mr. Porter. But I’ll tell you this for free: the statement that “heat cannot form a physically superficial discoloration” is unsupported by any kind of objective scientific data. It is in fact self-serving claptrap, and time will prove that I am right when I say that a thermal imprint (scorch) can be as faint and/or superficial as one wishes (see image below) right down to atomic and molecular dimensions. Can any of those gentlemen provide one piece of hard experimental evidence to demonstrate otherwise, or a theoretical foundation even for thinking there would not be a smooth continuum of image density down to zero discernible image?
What they seem to have forgotten is that energy transfer by thermal agitation (“conducted heat”) is a time-dependent process. If an image is more intense than one desires, there is always the option of reducing the contact time (or temperature), recalling that both are continuous variables that can be reduced in as large or small an increment as one desires.
I am frankly amazed that anyone with the most elementary science education could believe that scorching was some kind of all-or-nothing process. Would anyone dare place a hot iron down on a shirt, no matter how gingerly, if that were even remotely true?
That statement of Porter’s defies the most elementary physical and chemical principles regarding the nature of heat conduction and the initiation of chemical reactions in thermal and kinetic terms.
For new chemical bonds to be formed – in pyrolysis reactions, indeed in any chemical reaction involving molecules, existing bonds have first to be broken. The breaking of those bonds, with energy supplied by the Arrhenius activation energy, is a statistical process, governed by a frequency distribution of individual kinetic energies. That is why there is a smooth continuum in image intensity from easily visible to invisible, from finite depth to the most highly superficial modification at the atomic and molecular level.
No wonder scorching has been rejected all these years if the so-called big shots of Shroudology demonstrate an ignorance of the most elementary physics and chemistry.
If anyone doubts that scorch intensity is not infinitely variable, here’s an image from my experimental archive showing the result of serial imprinting as two metal templates (pencil sharpener, Ghana trinket) cool down:
Afterthought: Tue September 11:
Just in case exothermic hemicellulose pyrolysis is mentioned – a factor I suggested some months ago that might explain some of the peculiarities of the Shroud image, the half-tone effect especially: that phenomenon, if it exists, would operate only at the level of individual fibrils, allowing a highly-localised all-or-nothing reaction if the geometry is favourable. But there is no evidence that it could extend pyrolysis beyond the immediate zone of heating, as shown by those scorch images above with their sharp outlines.
(Btw: it may well be that oxygen is needed for exothermic pyrolysis. But the conditions for producing a scorch may well exclude oxygen for all intents and purposes: the initial effect of pressing a heated template against linen is to drive off the hydration shell as steam, and the latter is then further augmented by the ‘water of pyrolysis’ generated by chemical dehydration of linen polysaccharides that is then ejected down into the linen fibres as superheated steam. The latter is then in theory able to produce pyrolysis at a distance (“second face” on the obverse side?) but while there is abundant steam in the reaction zone there is unlikely to be little air – or oxygen. It may be oxygen availability that prevents hemicellulose pyrolysis from propagating far beyond the heated region – just a thought).