coating

Walter McCrone

One the flip side of the authenticity debate is the claim that one scientist, the late Walter McCrone (1916-2002), found red ochre (hematite) and vermilion (mercuric sulfide), common medieval paint pigments, and thus was able to argue that the shroud was painted. But that claim has since been proven wrong. Scientists—and we should probably only consider those who have actually looked at shroud fibers with microscopes and advanced scientific instruments—are quite certain about the chemistry of the images, and they are not made up of inorganic compounds McCrone identified through the lens of his microscope. The images are the result of a chemical change either to the fibers themselves or to some organic material on the fibers that was there before the images were made.

An analogy is in order. If you have a personal computer, you probably have an inkjet printer attached to it. When you print a picture, tiny droplets of ink are deposited onto the paper through tiny nozzles in a print head that passes over the paper. This is applied color. But it doesn’t really matter how color is applied with a paint brush, a pallet knife, drizzled on as Jackson Pollock did on his canvasses, powdered on as makeup is sometimes applied, or ink-jetted on. And it doesn’t matter if the colorant is paint, lipstick, dye or ink. The operational word is applied.

But there different types of printers that are inkless. Images are formed by a color producing chemical change to the media or to a coating on the media. One common type of inkless printer is a thermal printer. Thermal printers are often found in ATMs, cash registers and older fax machines. Paper that is coated with thermal sensitive chemical passes under a print head that heats tiny regions of the paper resulting in a chemical change that is evident by the change of color. This is not to imply that the images on the shroud were produced by heat. Many things can cause a color producing chemical change including other chemicals. Old newspapers that have become yellow, leaf stains on concrete, rust, these are all examples of color producing chemical changes.

Looking Stronger

Starting in 2003, new evidence began to appear in secular, peer-reviewed scientific journals that supported the Shroud of Turin's authenticity. From these journals we learn that the outermost fibers of the cloth are coated with a fine layer of starch fractions and various saccharides. In places, the coating has turned into a yellowish caramel-like substance. It is the change to this substance which forms the faint yellow images.

In the media and on the internet we are accustomed to seeing stark, contrast-rich photographs of shroud. But that is not what the images on the cloth are like. These have been enhanced. In reality, the yellow images are very faint. So faint are that some people report that they cannot discern them if they stand very close to the cloth.

The yellowish, caramel like substance suggests that a chemical reaction took place. Exactly what type of reaction, no one knows for sure. Perhaps fluids or gases emitted from a body reacted with saccharides. This can produce the color we see. But can it produce the distinct, highly-detailed images we see. If so, no one has figured out how.

We learn, also, of a faint second image of the face on the backside of the cloth. The second face supports the idea of a chemical reaction and adds more evidence that the image is not a work of art or a photograph.

The case for authenticity was looking stronger, as I saw it. Unfortunately some of the most intriguing evidence seemed dubious.

Is the Sudarium There?

There is, in the top layer of the cloth, an irregular raised spot, suggesting that there is something there between the lop layer and the bottom layer of the shroud. Is it the sudarium, the other cloth mentioned in John’s gospel wherein we read that Simon Peter “saw the linen wrappings lying there, ⁷and the cloth that had been on Jesus’ head, not lying with the linen wrappings but rolled up in a place by itself”? (NRSV John 20:6-7)

Biblical scholar Raymond E. Brown, a Roman Catholic Priest and professor emeritus at the Union Theological Seminary, a Protestant seminary in New York where he taught for 23 years, suggested that . . .

John is very careful about the state of the linen cloths (bands?) used to wrap the corpse, and the separate piece for the head. Their position may have outlined the original position of Jesus’ body which passed through them, leaving them where they were. (31)

It is, for the modern reader, perhaps a strange idea more apropos for Hollywood special effects. But what else do we expect if we are the sort of Christian who believes in a bodily, physical resurrection (many Christians do and many do not)? Did Jesus instead get up and remove his burial cloths. If his jaw had been bound closed with a chin band to keep the mouth closed, as has been common in burials throughout history, would he have untied it? Or did he pass through it? The question is only important because the raised shape in the drawing looking very much like it could be a knotted chin band, in just the right place for such an item. This is certainly consistent with Anglican scholar John A. T. Robinson’s view that the other cloth, the second cloth, was a chin band.

One Color, Different Density

That was a new aspect I had not considered. To see what Rogers meant by essentially identical spectrum-wise but different density-wise we need some lemon Jell-O. On a sheet of white paper put a very thin slice of the wiggly stuff on the paper. Beside it put a thick slice. Both slices have the same color but the thicker slice looks darker. This adds another element to the visual blending.

So not only are the images negatives (though not photographic negatives), not only are they height-fields, they are halftone or pixel formed at a fiber level. The best that we can say is, “that’s funny,” for all of these things so far defy logical explanation. And it doesn’t stop there.

The images are decidedly the result of a selective, color producing chemical change along distinct lengths of some of the cellulose fibers of the linen. Chemists who examined the fibers described the chemical change as an oxidation, dehydration and conjugation of polysaccharides (long-chain sugar molecules). It was once widely thought that this was a chemical change to the fiber itself, not unlike the oxidation and dehydration that takes place as linen turns yellow with age.  But Rogers believed he found a clear, ultrathin sugary coating on the fibers. He called it an impurity layer. The yellow color of the images, he thought, was caused by a chemical change to the impurity layer and not the fibers themselves.

Impurity Layer Disputed

Not everyone agrees with Rogers. Giulio Fanti and others think that the impurity layer that Rogers found is in fact the primary outer cell wall of the fiber itself and that the color change that makes up the image are to this outer wall.

But it seems that everyone who has directly examined the image on the cloth has concurred that the image is superficial to the topmost fibers of the threads of the cloth.

Flax Fibers

Flax fibers, from which the linen thread of the shroud is made, vary in thickness as well. But on average they are about 10 to 20 microns thick or about one-tenth to one-fifth the thickness of a typical human hair. Twist or spin together somewhere between 70 and 120 of these fibers and you get a single thread of the sort used for weaving the shroud’s linen fabric.

The layer or cell wall is thinner still. We said that Rogers had found an impurity layer and we might wonder how thick that is. Rogers had measured the thickness of the layer in places and found thickness ranging between 160 and 600 nanometers. That’s not microns; that is nanometers. Not millionths of a meter but billionths. That standard human hair that is 100 microns thick is 100,000 nanometers thick. If you could possibly slice that human hair lengthwise, from end to end, into 166 very thin slices, each slice would be as thick as the thickest coating Rogers found.  And the thinnest coating Rogers found was about one-fourth of that. The coating, in most cases is about as thin as the wall of a soap bubble drifting through the air. It is as thin as the glare proof coating on modern eyeglasses. Take a coin out of your pocket. Polish it between your fingers and thumb. It has a coating of oil on it as thick as the coating Rogers believes he has found on the shroud’s fibers. You can’t see it but it is there.

Hair is 100,000 nanometers thick. A flax fibers is about 15,000 nanometers thick. The impurity layer on the shroud is about 600 nanometers thick. The layer is only ten percent of the diameter of a red blood cell. That is thin, plain and simple.

Chemical Changes and the Impurity Layer

If Rogers is right about the layer, then there are essentially two ways to chemically change the color of the sugary substance to a yellowish color. One, familiar to every cook, is carmelization. Just toss some slices of onion into a skillet. As the sugars in the onion are oxidized by the heat, a chemical substance known as a melanin is produced. Melanin is responsible for the brown color as well as the wonderful aroma and taste that onions take on. Melanin is also the product that forms within the outer layers of your skin when you get a suntan from the sun’s UV rays.

Rogers Theory about Saponaria officinali

Rogers has a theory about how the impurity layer got onto the cloth. But to a scientist the right word is hypothesis. To test his hypothesis, he tried it out in a laboratory and it worked perfectly. He speculated that during weaving the threads on the loom were coated with starch to serve as a lubricant. This would make weaving easier and keep the threads from being abraded or unraveled at the edges. Because the cloth would be stiff from the starch, it was rinsed in a natural soap. Chemist that he was, it was it was by its binomial nomenclature, Saponaria officinalis. The rest of us call it soapwort, a wonderful natural soap still used to wash delicate linen fabric. 

After rinsing, the cloth was laid out in the sun to dry. As the cloth dried, water in the threads wicked their way to the surface carrying with them any remaining starch that remained and many different saccharides found in the soap. As the water evaporated into the atmosphere it left behind countless molecules of various sugars and starch as concentrations on the outermost fibers. Both sides of the cloth would have such a coating, but the side facing the sun would have the thicker concentration.

Cadaverine and Putrescine

Rogers was convinced that amine vapors emanating from a human corpse, principally very foul smelling cadaverine and putrescine, would react with the concentration layer of starches and saccharides. The reaction, a Maillard reaction, would cause a yellow or browning coloring of the layer covering the outermost fibers of the thread. But would it cause a distinctly clear, almost photorealistic image on a cloth draped over a body? Instinctively, intuitively, rationally people doubted that amine vapors could.

Rogers thought it might. Amine molecules are very heavy compared to many other gaseous materials. They behave differently. But do they behave differently enough? He conducted experiments and found that he could produce rough images at a small distance.

Superficial

Because both images are superficial (meaning there is no image or colorant of any kind between the two image layers on the extreme outer faces of the cloth) and because the images are in registry with each other, all so-far-proposed fakery proposals are moot. The images are not paintings and not some form of medieval proto-photography.

When the Shroud was examined in 1978, the backside of the cloth was not accessible. At that time, the Shroud was sewn to a backing cloth. Quoting from the IoP press release of April 14, 2004:

Because the images are extremely faint, the duo [Fanti and Maggiolo] has used an array of image-processing techniques -- including Gaussian filters, Fourier transforms and template matching -- to highlight human features.

They found that the face of the man that can be seen on the reverse of the Shroud matches that observed on the front. The image shows faint details of a nose, eyes, hair, beard and moustache . . . The Italian duo was also able to make out weak images of the man's hands, but could not produce images of his shoulders or back.

These new findings could help to shed light on the origins of the cloth but are more likely to fuel further debate over it. In 1989 (sic 1988), carbon-dating techniques revealed that the Shroud dated from medieval times and therefore could not have been used to bury Christ. However, many scientists have argued that the carbon-dating techniques used to study the Shroud were flawed.

Fanti and Maggiolo are now saying that the Shroud is unlikely to be a fraud because the image of the face is superficial on both sides of the cloth and only involves the topmost fibres of the material. "It is extremely difficult to make a fake with these features," says Fanti. 

While this discover of imaging on the backside of the cloth makes artistic and photographic methods significantly more implausible, it does lend credence to the possibilities that gaseous amines released by the body reacted with the carbohydrate layers. Some gases would have penetrated through the weave of the cloth and reacted with the backside carbohydrate layer. (And it does not rule out miraculous cause or effect).

Garza-Valdes and the Mayan Jade Artifact

In 1983, Leoncio Garza-Valdes, a medical doctor in San Antonio, Texas, and an amateur archaeologist, was examining a Mayan jade artifact that was assumed to be modern forgery. He was puzzled by lacquer-like coating on the object that he speculated might have been produced by bacteria. Garza-Valdes took the artifact to the radiocarbon dating lab at the University of Arizona. Scientists there were able to scrape off enough of the coating, as well as some bloodstains on the object, to give a date of about A.D. 400. The carving style suggested that the age should have been about 200 B.C.. However, if the bioplastic-polymer, for that is what it seemed to be, had been forming over the centuries, it would be a mixture of older and newer material. So perhaps the object really was 600 years older.

Following the carbon dating of the shroud, it occurred to Garza-Valdes that perhaps the fibers of the shroud were also coated with a bioplastic coating. And perhaps this also affected the carbon dating of mummy 1770. If ancient linen was subject to such a coating, then all bets were off on the carbon dating of the shroud until it was examined.

Garza-Valdes managed to inspect *** in Turin. Stephen Mattingly ****

The Ibis Mummy

Things were heating up. Harry Gove, a prominent radiocarbon dating expert from the University of Rochester in New York, who had wanted to be part of the carbon dating of the shroud and not been selected, was now involved. Ann Rosalie David, who had been part of the team that had studied mummy 1770, was involved as well. They met at the University of Texas Health Science Center in Austin. David brought a mummy of an ibis, a bird that the ancient Egyptians considered sacred. They had been careful to select one that seemed unlikely to have been rewrapped. They extracted samples of both tissue and bone from the bird as well as linen fabric from its wrappings. These they took to the National Science Foundation Accelerator Mass Spectrometry Facility at the University of Arizona, one of the same labs involved with the shroud’s dating.

The linen appeared to be newer than the bird it wrapped. And unless the bird was rewrapped—which seemed implausible to the four researchers—then appearances contradicted reality. They clearly saw something that seemed to be a bioplastic coating. But they entertained another possibility as well: the bird’s diet.

Conflicting Results

They noted that  radiocarbon measurements on charcoal and snail shells from the Graeco-Roman period in Egypt gave very conflicting results. The snail problem has surfaced. Not only might snails be a problem, but so to might anything that ate snails from water rich in depleted carbon like those found in artesian spring in Nevada.

But they seemed to prefer “bacterial infestation.” And the concluding paragraph of their paper makes this clear, but with a significant amount of caution.

Meanwhile, although the results of the present measurements include the possibility that the bioplastic coating observed on the cloth fibers of the wrappings of the ibis cause it to yield a radiocarbon age several hundred years younger that it true age, they are far from definitive. It would be premature to draw any conclusions about the true age of the Turin Shroud from these measurements. (49)

 U.S. News & World Report

It didn’t play out that way. If you were looking for a way to dispute that carbon dating of the shroud, you had it. Though it may have been premature of draw any conclusions about the true age of the shroud you could say, quite validly, that the sheen was off the carbon dating of the shroud. Unless Gove, et. al. were proven wrong, there was reason for reasonable doubt. Jeffery L. Sheler, writing in the July 24, 2000, issue of U.S. News & World Report, quotes Gove as saying, “There is a bioplastic coating on some threads, maybe most.” Gove goes on to say that if there is a sufficient quantity of bioplastic it “would make the fabric sample seem younger than it should be.”

Garza-Valdes and the Scanning Electron Microscope

Garza-Valdes had said: “With a scanning electron microscope, I found the fibers were completely covered by the bioplastic coating (polyhydroxyalkanoate) and by many colonies of fungi which usually thrive on this polymer...” But other scientists find this statement flawed For one thing, there is no way to determine the definitive composition of an organic material by scanning electron microscope. Garza-Valdes provided photomicrograph showing a "filamentous cell" that turned out to be an ultimate cell from the flax structure. Furthermore, it is well known that such polymers (they do exist on some ancient objects) obtain their carbon material from the host (fibers in this case) and not from the atmosphere, hence they do not significantly alter the C14 dating. Even if they could alter the date, the amount of material needed would need to be significant. On this point, Gove took exception with the bioplastic theory and agreed.

Chemistry Today Article

An article in Chemistry Today (August 2008) summarizes nicely:

Since the dating, many hypotheses have been proffered attempting to explain the C-14 results, which appear contradictory to a plethora of data pointing to a more ancient origin. An acceptable hypothesis of why the Shroud dated between AD 1260-1390 must satisfactorily explain the precise, statistically-determined angular skewing of the dates corresponding with the individual laboratories, with reference to the location of the sub samples received. The hypotheses of generalized ionizing radiation, thermal effects, environmental carbon monoxide enrichment and bio plastic coating are incapable of meeting this latter requirement, as is the premise that the cloth itself, is, in toto, medieval.

Superficiality

Chemists now know the coloration for the images is superficial at the topmost fiber surfaces of the cloth. The fibers are coated with a thin film of impurities made up mostly of starch. It is in this coating that the image resides. The visible image is the result of a chemical change, in certain places, that results in an observable change of color.

The coating can be physically removed from the fibers with adhesive tape. In fact, flakes of color can be seen where it separated from the fiber and stuck to tape used to collect particulate samples from the Shroud. You can see the thin coat of color through a microscope and it is hard to imagine how an artist could have accomplished this.

The images on the Shroud look ghostlike. They look scorched into the cloth. But chemically they don't resemble scorches. They don't contain the chemical byproducts produced by scorching.