- In 1970s a special eleven-member Turin Commission conducted several tests. Conventional and electron microscopic examination of the Shroud at that time revealed an absence of heterogeneous coloring material or pigment. In 1979, Walter McCrone, upon analyzing the samples he was given by STURP, concluded that the image is actually made up of billions of submicrometre pigment particles. The only fibrils that had been made available for testing of the stains were those that remained affixed to custom-designed adhesive tape applied to thirty-two different sections of the image.
- The technique used for producing the image is, according to W. McCrone, already described in a book about medieval painting published in 1847 by Charles Lock Eastlake ("Methods and Materials of Painting of the Great Schools and Masters"). Eastlake describes in the chapter "Practice of Painting Generally During the XIVth Century" a special technique of painting on linen using tempera paint, which produces images with unusual transparent features—which McCrone compares to the image on the shroud.
- Thus, when in 1979, Walter McCrone, a world renowned forensic microscopist, claimed that he found paint on a few Shroud fibers, I didn’t notice the story. McCrone, having noted that the shroud had suddenly appeared in 1356 in the hands of a French knight who would not say where it came from and that a local bishop soon thereafter claimed that an artist “cunningly painted” it, declared it a painted fake.
- This hypothesis was declared to be unsound as the X-ray fluorescence examination, as well as infrared thermography, did not point out any pigment. It was also found that 25 different solvents, among them water, do not reduce or sponge out the image. The non-paint origin has been further claimed by Fourier transform of the image: common paintings show a directionality that is absent from the Turin Shroud.
- John Heller and lan Adler examined the same samples and agreed with McCrone's result that the cloth contains iron oxide. However, they concluded, the exceptional purity of the chemical and comparisons with other ancient textiles showed that, while retting flax absorbs iron selectively, the iron itself was not the source of the image on the shroud. Other microscopic analysis of the fibers seems to indicate that the image is strictly limited to the carbohydrate layer, with no additional layer of pigment visible.
- The notion that such super-thin images were painted is preposterous. Yes, it is true that one scientist did look through a microscope and find components of what might have been paint. And because of this he concluded that the Shroud was painted. Walter McCrone was a world-renowned microscopist, deservedly so. He was a true scientist and he knew his craft well. We should not doubt that he found iron-oxide and mercury-sulfide, both constituents of paint. But there are many reasons why such chemical particles might be found on the Shroud. Water used for retting flax introduced iron. And centuries of dust, particularly dust in churches with frescoed ceiling and walls, introduced all manner of trace contaminants. All other scientists who examined the image fibers -- many of them every bit as renowned and qualified -- have disagreed with McCrone. There is, simply, an insufficient amount of paint constituents to form a visible image. Spectral analysis proves that. So does the now certain knowledge of the image bearing super-thin film. Ironically, McCrone identified the super-thin starch substance that ultimately became part of the proof that his conclusions were wrong.
- I learned that McCrone’s identification of paint was a subjective judgment. More sensitive tests, some undertaken at the National Science Foundation Mass Spectrometry Center of Excellence at the University of Nebraska, proved, beyond a shadow of a doubt, McCrone was wrong.
- In 2004, a startling discovery was made. A faint second face was found on the back of the Shroud. This second face was directly behind the face on the front of the cloth as though paint or stain had soaked through. But when we probe between the two facial images, when we look at the interior of the threads, when we examine individual fibers, we discover that nothing has soaked through. The faces are thin and superficial to the extreme outer surfaces of the Shroud.
- Whatever the Shroud of Turin is, it is not a painted, medieval fake-relic. The unmistakable images of a crucified man were not created by any known artistic method. And thus, the honest skeptical inquirer will turn to history for clues. In doing so he discovers that newly found, newly translated and newly interpreted documents provide a plausible historical scenario for something that is not a medieval fake-relic.
- 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 layer of starch fractions and various saccharides. In places, the coating has turned into a caramel-like substance, thus forming the images. This suggests a chemical reaction took place.
- There have been claims for a long time that the Shroud cannot be the work of an medieval artist. However, this has been shown to be wrong a number of times. Using material, such as red ochre, that had been a common pigment since around the 9th century, Walter Sanford and Joe Nickel had created quite similar images in the early 80s. Nickell had used a rubbing technique with red ochre on linen cloth spanned over a bas relief, which was also published in the Skeptical Inquirer (Vol. VI/3, Spring 1982) featuring the Shroud replication on the cover page. Last year, chemist Luigi Garlaschelli (CICAP) created a whole body image of the Shroud. which was artificially aged to show the additional yellowing coloration due to age. Though it will never be possible to have a 100% replica – after all, no one can completely “copy” a van Gogh – these replicas have shown that an artist using techniques and material available to him, could well have produced an original piece of work, such as the Shroud of Turin. It is of course not a forgery , which would require another original to work with, but rather a creative artist’s original of the 14th century. As for the pro-Shroud proponents, none have produced anything even remotely plausible as to how such an image could have formed without human intervention in a burial situation.