Is Colin Berry going to be able to show how a medieval forger did it? He thinks so. He explains in a new posting, let’s focus on that hemicellulose coating on the linen fibres:
Yup, I now believe that hemicellulose is the key to understanding the nature of the image on the Turin Shroud – and yes, the latter has most if not all the characteristics a heat-induced scorch, but a highly selective one that was largely confined to the hemicellulose coatings of the fibres, leaving the cellulose cores largely unaffected.
Why do I say that? One of the major challenges has been to explain the highly superficial nature of the Shroud image, reckoned to be a mere 200nm (that’s approximately the thickness of gold leaf) , so thin and weakly attached that it can be stripped off with adhesive tape, as described by the late great Raymond Rogers, the so-called half-tone effect.
Let’s do a thought experiment to see how that Turin Shroud could have been produced using simple technology that was available in medieval times, supported by a theoretical framework that is in tune with physics, chemistry and botany.
But there is another curious detail about the Shroud image which is capable of explanation in the hemicellulose model, and once we have addressed that we shall be in a position to explain the so-called “half tone “effect.
Whereas the pyrolysis (“heat-induced degradation”) of cellulose is endothermic, i.e. requiring constant application of heat to be sustained, the pyrolysis of hemicelluloses is reported to be exothermic ( see previous post) In other words, once started it can, in principle (thermodynamic principle that is) be continued after the initial source of priming heat has been removed or gradually conducted away). A burning match is a model: provided it is held with the lit end slightly down, it will continue to burn, because heat from the flame provides the energy for pyrolysis of fresh wood, carbonising it, releasing more flammable gases, allowing more combustion, more flame, more pyrolysis, and the potential for a runaway reactions . I believe there is a low-level (flameless) conflagration, a micro-runaway reaction if you like, when hot metal encounters hemicelluloses-coated fibres: the hemicellulose pyrolyses (“chars”) where it is in immediate contact, but a spreading zone of pyrolysis then runs around the complete encircling cylinder of hemicelluloses, leaving a bare, largely untouched core of cellulose. That would explain the thinness of the image (representing the primary cell wall/hemicellulose thickness) but would also explain the fact that the image is in the ENTIRE coating of each of the (relatively few) affected fibres.
We are now in a position to understand the half-tone effect. The latter description refers to a curious feature of the Shroud image. It might have been expected that where the image is most dense, each fibre would show a greater degree of coloration. That is not in fact the case. Image areas are a mixture of coloured and uncoloured fibres. A denser image represents a greater number of coloured fibres per unit area, but coloured fibres are all said to be much the same hue. In other words, there is an all-or-nothing effect about image-forming at the level of individual fibres. The hemicellulose model accounts for that neatly. . . .
Or will it be just another in a long string of failed attempts to duplicate the shroud? If he only does thought experiments, will he nonetheless create a legend, one that many people will buy into. Will he be remembered as the scientist who did it, almost did, could have done it?
Much more, so read the full posting on his blog: The Shroud of Turin – let’s focus on that hemicellulose coating on the linen fibres … It could explain a great deal | Spotlight on that Shroud of Turin – without all the hype
In theory there is no difference between theory and reality. In reality there is.
I like the theory, Colin…I never knew that the outer casing was darkened all the way around like that (but I’m fairly new to this). A run away reaction could explain that and traversing along the fibril.
However I still think the explanation of the image on the other side is weak, as whatever heat is conducted has to go through the body of the material and if its hot enough the pyrolyse the hemicellulose on the other side, its hot enough to pyrolyse the hemicellulose of the in-between fibres and darken them as well(which it doesn’t). And again I think you’re pulling a fast one with the supposed high conductivity of cellulose, which the tables show isnt the case.
“I never knew that the outer casing was darkened all the way around like that (but I’m fairly new to this). A run away reaction could explain that and traversing along the fibril.”
Yes, it’s all in the excellent paper by Fanti et al (2010) : “Microscopic and Macroscopic Characteristics of the Shroud of Turin Superficiality”, easily googleable and available in full for free,
However I still think the explanation of the image on the other side is weak, as whatever heat is conducted has to go through the body of the material and if its hot enough the pyrolyse the hemicellulose on the other side, its hot enough to pyrolyse the hemicellulose of the in-between fibres and darken them as well(which it doesn’t).
Methinks someone has forgotten the difference between heat and temperature, It’s not enough to have the right temperature. There has to be sufficient thermal capacity for the hemicellulose-coatings to be “ignited” – possible with hot backing sand, with ample mass, probably not with light cellulose fibres en route (but the latter can still conduct, as they do to high thermal capacity water in that trick with the bag.
And again I think you’re pulling a fast one with the supposed high conductivity of cellulose, which the tables show isnt the case.
I did not make, or mean to make, a big thing about “high”conductivity, certainly not in terms of classic good conductors like metals, and Irest assured I am not planning to market cardboard saucepans anytime soon. Don’t you think it impressive that the cellulose of a paper bag is able to conduct heat at a sufficient rate to boil water, and to so so without any sign of degrading? In that sense the paper is a “goodish” conductor, good enough to dissipate the heat from a naked flame into water on the opposite side of the paper. Had Raymond Rogers been aware of, or thinking of that trick, would he have been so ready to dismiss scorching as a mechanism, based on the juxtaposition of image fibres with cellulose that looked entirely normal under the microscope? But that sharp transition between charred and pristine now needs to be re-evaluated anyway in terms of heat-labile hemicellulose adjacent to more heat-refractory cellulose. That’s not to belittle Rogers – far from it – since it was his adhesive tape studies that first alerted us to the superficiality of the image, which as I’m sure you know he interpreted as attached to adventitious starch and saponins, rather than a more mundane botanical explanation in terms of primary cell wall and hemicelluloses. So near yet so far as they say… May he rest in peace…
Colin, I even think, for your theory to work to sustain the exothermic reaction until it reacts all the way around the cylinder, it needs that cellulose have low thermal conductivity because otherwise the heat gets removed from your reaction zone. Still I like the theory’s ability to explain the “full on/ full off” image characteristics.
If you look at that graphic (top of Dan’s post) which I purloined off another site, says he shamelessly, the primary cell wall is a highly open structure – mainly unoccupied space in fact. Its job after all is to stretch and resist cell turgor (it being the osmotically-imbibed water that confers rigidity to the stems of non-woody plants, not the cellulose as often believed).
So if you think of the hemicellulose chains as being like fuse wire, and the cellulose fibrils like steel scaffolding, then one can fizz away merrily largely or entirely independent of the other with negligible heat transfer between the two…
…Err, no. Your science is skewed again, Colin. For heat to flow from hot metal side of cloth to hot sand side of cloth, there has to be a temperature gradient, so if its hot enough to send facial information and pyrolyse onto the sand side, its hot enough through the middle of the cloth to pyrolyse as well. So if metal is say 350 and sand is 300 and pyrolysis kicks in at 320…for the sand side to get a facial marking, it must have risen to above 320 due to heat flow from the metal side (and any cloth in between will be similarly scorched as due the temp gradient it must be above that 320 temp). So you are asking of your forger to not only be a superb artist, anatomist, historical expert but also a thermodynamicist capable of making heat go in the wrong direction from cold to hot. A tall order if I may say so!
So though I like part of your theory, it only partially explains the Shroud image and I think it would also struggle with the blood markings as well. I know it a bit like asking you to gnaw off your own leg, Colin, but would you concede that the Shroud is not just a mystery to the gullible as your blog implies, its a puzzle to seasoned observers, sceptics and scientists as well?
Well, not only do I have a Plan B where the image on the reverse side is concerned, but you’ll have to take my word that it was Plan A right up to a few hours before posting! I could wheel it out now, but it would look like I was backing down on the heat/temperature thing. I’m not. Think about the static electricity when you pull a woollen jersey over your head. I had such a belt a few days ago, when the humidity was down in the mid 20s, but it did NOT singe my hair, or if it did the missus has not commented (and I would have smelt it surely). An electric arc has a temperature in thousands of degrees Celsius, but will not burn if there is insufficient electrical or thermal energy to cause pyrolysis..
“… would you concede Shroud is not just a mystery to the gullible as your blog implies, its a puzzle to seasoned observers, sceptics and scientists as well?”
Again, I don’t have to concede a thing, since I agree wholeheartedly with the sentiments expressed. But being a scientist (well, a retired one) I believe that the mystery can be unravelled by patient application of known scientific principles.
My starting point, back in December last year, was that appalling paper by Di Lazzaro et al and the press reports that accompanied it, given it assumed that the Shroud image had been produced by some kind of electromagnetic radiation at a distance, in the absence of any means of focusing it to form an image, and then making a huge song and dance about producing a small superficial scorch mark on linen with their death ray high energy uv laser (like something out of a Bond film). It’s what I call Mickey Mouse science, and will continue to do so until I see some correctives appear in the media, preferably from the authors themselves. 2011 ended as a black year for science… Those Italians were using their hi-tech toys to take us back to a pre-Enlightenment era of magic and superstition. New Age Endarkenment?
Nope, it’s nowt to do with religion or Christian beliefs, and EVERYTHING to do with preserving the credibility of science, and the scientific method, which is NOT about testing dud hypotheses that attempt to make a mockery of scientific laws and principles …
Still doesnt make much sense to me, Colin…One of the good things about your theory was that hemicellulose was exothermic, and so it had a good ability to self sustain once above the pyrolysis temperature.
But now you’re saying that though the energy supply through the thickness of material is enough to bring the sand interface up enough degrees to pyrolyse but its not enough to keep in pyrolysis any reaction inside the material (that should have some ability to self sustain in any case)?
Remember that the sand bed is still effectively a large heat sink relative to the pyrolysis temperature, more likely to keep the temperature of cloth next to it below pyrolysis. If the energy coming from the metal side is enough to raise this heat sink temperature sufficiently, then its enough to keep internal pyrolysis going.
I am await your Plan B with anticipation.
Well, one wins some, one loses some.Trouble is, it may be years before one knows for certain on which details one was correct or not. But we are talking here about details, not principles, so let’s not get too bogged down in the detail.
Plan B is very simple. Given the cloth is a (“nominal”) 0.34 mm thick, then infrared radiation could be making a contribution at such short range if there were to be a dark-coloured absorber available, as indeed there is. Infrared could be trapped by a backing semi-opaque sand-bed and then bake the adjacent linen to produce that faint fuzzy image on the reverse side. Passage of infrared rays through the linen would be assisted by preliminary scorching by contact, reducing white-surface reflection/scatter of incident radiation, thus creating a partial black body absorber/emitter. Prediction: it might be a somewhat grainy image ;-)
“principles, so let’s not get too bogged down in the detail”
Well thats the big problem is that the devil is in the details.
Concerning Plan B, let me give a simplified model of what you mean (do tell me if this is not what you mean).
Suppose for simplicity we have some simple image say shaped like a letter E, and replace the cloth by layers of paper. Then we get a darkened E shape scorched onto the top surface of first sheet of paper, and then this heats up more and re-radiates ir light, say through 3 more sheets of paper at the bottom of which is a black sheet of paper (representing the sandbed), that black sheet gets a bit hotter where a fuzzy image of the E would be, and that extra heat is enough to trigger pyrolysis on the back surface of the final white sheet (which has been kept at a temperature just below pyrolysis normally).
Nice idea but with some big problems;
1)the intervening light layers of paper who reflect much of the ir back, perhaps with multiple reflects giving a very fuzzy image
2)the faint scorched E is only very faintly different from the rest of the paper so the temp difference is going to be very slight on the black sheet, and additionally during most of the scorching time there is even less difference.
3)the black sheet (ie the sand bed unlike the metal) is hard to evenly heat, and ensure is just below pyrolysis (and we are talking about the days before decent thermometers)
4)the ir heat that gets to the black sheet has to first heat this up (and we’re talking a heat sink of sand), before it can start to pyrolyse the last sheet.
I’m not sure this is any better than Plan A, sorry.
Sorry, you’ve lost me there Ron, what with those 3 sheets of paper. What’s wrong with a simple model for starters that has, er, like, you know, just one sheet of linen?
Well the sheets where meant to show that the intervening layers of threads will do a fair bit of reflecting back. But stick to a sheet of linen if it helps…you still got major problems to address but perhaps one you can try to solve is how you going to heat up the sand enough just from your faint difference in ir, to distinguish an image on the backside of the linen. And all this without burning through more than 200nm of the top layer.
Better start on Plan C
We don’t seem to be making huge headway with this conversation, do we Art (sorry about the “Ron” slip above)? Would you not agree that an hypothesis (indeed two hypotheses) offering a possible explanation for an odd phenomenon is better than no hypothesis at all – at least within the “narrow” terms of reference of science. I consider that each of my two hypotheses are testable – the first by placing a temperature sensor at the linen/sand bed interface, the second by placing an infrared sensor there, and taking readings before, during and after the making of a thermal “footprint” on the top surface.
I haven’t even posted here and yet I’m still in your mind Colin, LOL. Hope your not speaking my name out loud in your sleep! We wouldn’t want to worry the misses ;-)
Well I’m keen on getting workable hypotheses and at least one didnt seem to come within that category ( involving dubious heat flows in wrong direction) but please go ahead and test, its always the best way as nature will often surprise us.
Anyway I might have another hypothesis, but I need to find out from you (as you have access to Fanti’s paper about the 2nd image)…are we sure that 2nd image is also due to the same mechanism (ie the darkening of the outer sheath of the fibril). If it wasnt, perhaps if the linen were wet whilst touched on the bas-relief, any impurities in the cloth or loose scorch marks would be steam blasted, where contact was greatest, through to the other surface, appearing as a faint image there (but not on outer sheath of fibres). I’m not sure if this is any better(making a mess of the blood stains as well), but it would perhaps explain why the internal material isnt darkened.
Comments are closed.