Is Fluorescence Still in Question?

Which compels us to revisit Charring, fluorescence and image-forming
mechanisms. Beware Shroudology’s junk science and flawed logic…
on Colin’s blog

imageJonathan in Houston writes:

Before moving to Houston I worked as a tech in a crime and accident lab for twelve and a half years and I can tell you we found scorches on cloth so light you could not see them. Even so they fluoresced. We also found very visible scorches that did not fluoresce at all. So what Dr. Berry wrote about light and heavy scorching makes a lot of sense to me.  I do not recall anything about linen specifically and I do not know about the effects of age.  I wonder, is there a definitive study about the scorching on the Shroud? Did anyone quantify and chart fluorescence at the edges of different burn marks and beyond the edges of the burn marks?  Did anyone experiment with a control sample of untreated linen cloth that was not modernized for brightness or wettability?  Did anyone examine other ancient linen cloths that have been burned in places?  BTW I am not a chemist.

I think this recent comment by Colin Berry is what Jonathan is referring to:

image. . .  Polymerization may well be the key to understanding the basis to the fluorescence of the 1532 burn marks, and why (in passing) it’s a mistake to imagine that the TS cannot be a scorch through lacking fluorescence.

The fact that the 1532 burn marks still fluoresce almost 5 centuries later suggests the molecules responsible for the fluorescence are of relatively high molecular weight, almost certainly solids, or they would have evaporated away by now. Candidate molecules, if one is looking for uv fluorescence and high molecular weight, say 300 or greater, would be the polycyclic aromatic hydrocarbons, containing fused aromatic ring systems (5 or 6 carbon). Are there mechanisms by which they could be formed in linen exposed to very high temperatures? Yes there are. Here’s the reasoning. The ultimate product from deep scorching of linen is black charcoal, i.e. microcrystalline graphite. While the latter is almost pure carbon, its graphene sheets are polycyclic aromatic in structure, ie. fused benzene rings, and there is no way they could be formed from cellulose etc of linen except via a polymerization process from low molecular weight monomers. But forming those monomers, whether furfural or some other product of pyrolysis, requires high temperatures, considerably higher than those needed merely to leave a scorch mark on linen.

Without labouring the detail, or going over old ground, the structure of the flax fibre is probably the key to understanding the difference between light scorching (no fluorescence) and heavy deeper scorching (intense fluorescence). Light scorches probably pyrolyse selectively the carbohydrates of the primary cell wall, notably the chemically reactive hemicelluloses. Heavy deeper scorches affect the cellulose in the core of the fibre, requiring a considerably higher temperature, and generating the monomers that are needed for polymerization on the graphite pathway terminating in charcoal that are responsible for intermediate uv fluorescence.

Take away message: it’s false logic or bad science or both to imagine that the fluorescence of the 1532 burn marks precludes heat as a mechanism for TS body image formation. Barrie Schwortz, Russ Brault and other pro-authenticity proslelytizers please note: your playing the ‘fluorescence card’ may impress your audiences, but they don’t impress this retired researcher who has experience of tracking fluorescent compounds as part of his research career, and knows rather more than you do about the complexities of the fluorescence phenomenon, and why it can never be used to prove or disprove a case if you know NOTHING about the chemical identity of the fluorescent species.

Which compels us to go over old ground and revisit Charring, fluorescence and image-forming mechanisms. Beware Shroudology’s junk science and flawed logic… on Colin’s blog wherein we read:

The non-fluorescent body image on the Shroud is a pale sepia colour.  It may or may not have been the result of mild scorching (I happen to believe it is a light scorch). But the fluorescent, heavily charred regions on the Shroud are the result the 1532 fire etc. There is no inconsistency whatsoever between these two findings. All that remains to be done is to offer an explanation as to why one fluoresces and the other does not, ensuring that it is a TESTABLE  and potentially FALSIFIABLE explanation, i.e. a SCIENTIFIC explanation.