imageA reader writes:

Dr Berry wrote, “here’s the evidence” to claim that Dr.  Di Lazzaro’s was wrong when he said, “Heating linen cannot give a superficial coloration”. And then he provided nothing but a photograph of a faint scorch mark he made. So what! My mother used to make faint scorch marks on linen with a cheap electric iron. Just because it is faint does not mean it is superficial. In fact, I’ll eat my hat if it is. Why do you even give Dr Berry any notice? (link added by me)

Colin actually wrote of the image he created on linen:

“Heating linen cannot give a superficial coloration” says Dr. Paolo Di Lazzaro. Oh yes it can – and here’s the evidence…

He shows a photograph (here is a link to the photograph that he doesn’t want me to show in this blog) of a faint scorch and some char on a piece of linen and proclaims:

Why then did the linen under the hot metal not char like the strip that was kept in the oven? Why is the image so superficial?

Superficial? How does he know it is superficial? What does he mean by superficial? Is he equating the word with the word faint? Of course, the image on the shroud is faint. But it is also superficial in scientifically observed, quantified ways. Paolo Di Lazzaro, based on scientific experiments conducted at ENEA, also provided a comprehensive explanation.  I have provided a copy of a letter from Paolo, below.

When Colin made his preposterous claim, Paulette reacted quickly:

What in the world is Colin thinking? Where are his measurements? Does he even know what superficiality means?

There are several aspect of the superficiality of the image that cannot be ignored. The first three are absolute superficiality characteristics of the image. The last three are likely consequences of that superficiality.

1. The image does not penetrate below the topmost two or three fibrils of the yarn
2. The discoloration of the fibrils themselves, presumably from dehydration and oxidation, is between 200 and 600 nanometers thick (billionths of a meter).
3. The medulla of the fiber is clear in both image and non-image fibrils
4. The image can be removed from a fibril with adhesive tape.
5. The image doesn’t fluoresce in UV light.
6. The halftone effect evident in the image is from striated color patterns.

Then Ron wrote:

Paulette; please let’s not quibble about the details, Colin Berry has MANAGED to scourch linen here…. ;-)

Ron even added the smiley. But Colin got upset. He accused Ron of a flippant and supercilious put-down. Does Colin not remember that he accused Paolo Di Lazzaro of Mickey Mouse science without offering a reason? How flippant and supercilious is that? Colin first set the tone when he started blogging about the shroud with one arrogant statement after another. Ron is perfectly justified in saying what he did. I would have said it if I’d thought of it. 

So where is the evidence, Colin Berry?

And here is the explanation sent to me by Paolo Di Lazzaro on February 21 of this year:

Dear Dan and All:

I checked the idea of Colin Berry in the website you quoted. In short, from a physics point of view, his model is untenable, especially concerning the depth of coloration. Let me explain why.

Berry wrote: “The scorching will initially be confined to those parts of the fabric that are in immediate contact with the hot metal; no air gap is permissible, since radiated heat will not scorch white linen. What is more, the scorch will be confined to the outermost fibres of the thread, because the scorch will tend remain trapped within the first-encountered fibres, rather than being able to “jump across” to adjacent fibres. Why is that? It is because the resistant cellulose cores that are unaffected are able to conduct away heat rapidly, bringing the temperature of the hot template down to below that which will induce scorching Is it realistic to suppose that cellulose fibres could conduct away heat without themselves becoming degraded? Yes. I believe it is.”

It is quite easy showing the above assumption is wrong, and it is one of the few cases where it is faster doing the experiment than to explain the theory. According with a paper quoted by Berry, the onset of pyrolysis in hemicelluloses is at about 220°C. We have heated a 5-cents euro coin at about 230 °C in contact with a linen cloth. Just 5 seconds after the coin reached the max temperature the whole cross section of threads in contact with the coin was colored. After15 seconds all the thickness of the cloth was colored and the round shaped image of the coin appeared on the opposite side. After checking in our Lab, we repeated this easy and small-size experiments in the RAI3 TV studios (GeoScienza) to demonstrate that heating linen cannot give a superficial coloration. See starting from the minute 16:30.

After the experimental demonstration, let’s approach the basic elementary physics that explain why the idea of Berry is untenable, and heat cannot produce a superficial coloration.

The hot metal transfers energy(heat) to the primary cell wall (pcw) of the linen fibrils by contact. From a microscopic view, transferring energy by contact means the hot (i.e. fastly moving)atoms of metal hit hemicelluloses molecules transferring momentum, thus increasing both amplitude and velocity of the motion of hemicellulose molecules around the equilibrium position (centroid). As a consequence, hemicellulose increases its temperature.

In the regions of contact between pcw and cellulosic medulla, we still have a transfer of heat by contact, like in the previous metal-pcw case. The temperature of the medulla will increase. In the region where there is no contact (e.g.,a small air gap between pcw and medulla) we have heat transfer by irradiation.In fact, every material emits radiation having a spectrum peaked at a wavelength which depends on its temperature: the higher the temperature, the shorter the wavelength. This is the well known phenomenon of the black body emission, governed by Planck’s law, Wien’s law and so on (first year exam for students of Physics, Mathematics, Chemistry, Engineer).

As an example, at 20 °C the walls of a room emit radiation with a broad spectrum, peaked in the far infrared at about 10-micrometers wavelength. In the case of hemicelluloses at 200 °C the pcw emits infrared radiation peaked at 6,1 micrometers. In the case we are considering, the 6-micrometer wavelength will interact with the cellulose of the core of the linen fibril (medulla), exciting vibrational levels of cellulose that decay in heat thus increasing the temperature of the medulla.

In addition, a well known optics law tells us the penetration depth of the interaction between radiation and medulla cannot be smaller than the wavelength, that is, not smaller than 6 micrometers in this case. This fact alone explain why infrared radiation cannot produce a superficial coloration of fibers.

By the way, it is not possible that “the resistant cellulose cores that are unaffected are able to conduct away heat rapidly” (see above Berry’s statement) because of elementary fluid dynamic equations (a classical engineering problem), of a not convenient area/volume ratio of cylinders (elementary geometry) and because Berry assumes a exothermic pyrolysis of cellulose, that is,by definition, a runaway process, extended in time.

In summary, when heating a linen cloth by a hot metal in contact, well known physics models foresee the pyrolysis of the whole fibers and threads, and this is exactly what we observe in the experiments.

Useless to say, it is all the approach of Colin Berry to find a middle age technology able to create the Shroud image that is hopeless: just consider the half tone effect. It could not have been made by medieval forgers because they would need a modern microscope to observe and then control their micrometric-scale coloration.

All the best