The root source of this information is a November 1998 B.A.R. article by Walter C. McCrone in which he says:
"Nearly 20 years ago the Catholic Church invited me to determine chemically what the image is on the Shroud of Turin."I obtained 32 samples from the shroud: 18 from areas where there are images (both of a body and of bloodstains) and 14 from non-image areas (some from clear areas that served as controls, others from scorch and water stains caused by a fire in 1532). The samples were taken with squares of sticky tape, each of which exceeded a square inch in area and held more than 1,000 linen fibers and any materials attached to the shroud.
"They were excellent samples. I used standard forensic tests to check for blood. I found none. There is no blood on the shroud.
"To determine what substances are present in the shroud images, I conducted tests based on polarized light microscopy. I identified the substance of the body-and-blood images as the paint pigment red ochre, in a collagen tempera medium. The blood image areas consist of another pigment, vermilion, in addition to red ochre and tempera. These paints were in common use during the Middle Ages."
So McCrone in 1998 is talking about tests he conducted in the late 1970s or early '80s. It would be interesting to learn how and why McCrone's tests were in error.
McCrone refused to submit his findings to peer-review, pubished his work only in his own vanity self-published in-house magazine The Microscopist actively attempted to prevent other scientists from having access to the samples. He is not an expert on blood, he is a chemical microscopist who based his findings on optical observation only. His work has NEVER been duplicated by any other scientist working with much more sophisticated equipment and has been falsified many times over by that more sophisticated equipment. . . including employees at his own McCrone Research Associates using Scanning Electron Microscopy which found no sign of the natural Red Ochre that McCrone claimed he saw in his optical Microscope.
His "standard forensic tests to check for blood" often will not work on blood that is even as old as twenty or thirty years old, according to many forensic pathologists, so why would you or McCrone expect them to work on 2,000 or even 700 year old blood? Unless you can get it to solubilize, the tests will not work and blood that old is VERY hard to solubilize... as Drs, Alder, Cameron, and Heller, who are experts on blood will tell you, and who have succeeded in solubilizing it AND performing definitive tests that prove that it is, indeed, blood that non-expert McCrone, a microscopist, who has his one optical microscope tool at his disposal was incompetent to use.
In science, it is usual, customary, and totally appropriate to toss out findings that have been falsified by later findings and/or failure to be replicated by peers. If it cannot be shown again, or a test cannot be shown to be repeatable, then it is likely NOT TRUE. McCrone's claim of Red Ochre and Vermilion paint in a 10% solution of Egg Albumin Tempura matrix is just such a claim... both non-replicated and falsified by previous and later findings. Ergo, it must be tossed out... and has been. It belongs in the dust bin of other scientific ejecta as flogiston, phrenology, and global warming. A list of McCrone's failures due to his allowing his atheistic biases to get in the way of his science:
1> McCrone's findings were never peer-reviewed because he refused to submit them for peer-review.
2> McCrone broke his signed agreement with the Shroud of Turin Research Project to submit his findings for peer-review before publication.
3> McCrone broke his contract to publish only in approved peer-reviewed scientific Journals by publishing without approval in his in-house vanity magazine, The Microscopist, edited and published by Walter C. McCrone, claiming it was peer-reviewed by McCrone Associate employees
4> McCrone's findings were never replicated by any other researcher. No other microscopist, either optical, or electron, has found the Red Ochre or Vermilion associated with the blood stains that McCrone claims is present. The evidence is that McCrone saw what he WANTED to see, not what was there.
5> McCrone's findings have been falsified numerous times, by numerous scientists, more qualified than McCrone, working IN THEIR FIELDS, with work that has been replicated, and confirmed by independent testing with different approaches using different tests.
6> Even McCrone changed his story so many times it had become a running joke among Shroud researchers as to what type of Iron Oxide McCrone was claiming he saw on the Shroud this year.
7> McCrone refused even his employees permission to see, or test the samples in his possession with more sophisticated equipment because, saying, (paraphrased) in multiple interviews, "I want to to re-establish the primacy of the optical microscope as a research instrument, and using the optical microscope to prove the Shroud nothing more than a beautiful painting will do that."
8> McCrone refused to return STURP Shroud samples loaned to him at the conclusion of his research to STURP control and threatened to sue when STURP reclaimed "his" samples, irrationally claiming they had become his personal property, because of his research and findings.
McCrone has been discredited completely on his claims of Red Ochre paint and Vermilion as the blood stain on the shroud... by such tests as X-ray photomicrospectroscopy... a much more specific test that looking through an optical microscope and saying, "Gee, that looks like Red Ochre and Vermilion." When an X-ray photomicrospectrograph says there is no HgS on there, there is NO Mercuric Sulfide on there... no matter WHAT Walter C. McCrone claims he sees through his little microscope. Or how many times in 1998 or how many times Joe Nickell writes that it is there... IT IS NOT THERE! Follow the science, not the popular press.
The X-Ray spectrograph work was done in the early '90s... but still disingenuous people WILL trot out McCrone claiming him as definitive proof that the Shroud's blood stains are Red Ochre and Vermilion paint... and Joe (I'm a skeptical inkwirer) Nickell will write it in another book in the last few years, ignoring the good science, and claiming McCrone (an Atheist) as the only TRUE scientist involved and everyone else a "pseudoscientist" doing research from faith bias, despite many of them being Jewish (Adler, Heller, Schwortz) or agnostic (Rogers, Brown) or others who are Christian of various faiths... and YOU, BroJoeK, will dutifully find a citation to present on FR as though McCrone's outdated, falsified claims bear some probative weight in the discussion. they simply do NOT because McCrone's findings have been falsified and belong in the GARBAGE.