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I saw the post by Davefoc, and got this in response:
http://shroud.com/pdfs/chronology.pdf
Specifically Entry 39 (regarding Mechthild) and 45
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Hello Pierson5 and welcome,
With respect to entry 39 and 45
I think this may refer to entries in the addendum to the list you linked to (
http://www.shroud.com/pdfs/addendum.pdf). I looked at entries 6, 7 and 13 in the addendum with the idea that they might correspond to the entries 39 and 45 you referred to.
None of these entries offers any evidence that the C14 sample area was patched. They do include the fact that the C14 test protocol was changed. I think this is an accepted fact with regard to the C14 testing of the shroud. Nothing about that is evidence that the testing as done was not accurate and reliable.
General comment about the main list with 32 entries that Pierson5 linked to
This is a long list and without considerable effort it is difficult to know what the list consists of and what it's value is with regard to the reliability of the C14 testing. If the entries are well thought out, intellectually honest arguments then it might be provide powerful evidence that the C14 testing was in error. If the list consists of cherry picked evidence with analysis slanted to finding any tiny shred of a plausible claim that the C14 testing was in error then it is just a routine screed done by shroud authenticity believers that has no probative value as to the reliability of the C14 testing.
I am not going to take the time to figure out which it is, but if there is somebody that wanted to go through the list and find what they believe is analysis or evidence that supports the claim that the C14 testing was in error I at least would look at it and I suspect several other people that have participated in this thread might also.
I did arbitrarily pick one of the entries to look at in detail. This was item 32, the last entry in the list. This is a reference to this 1997 paper, "A problematic source of organic contamination of linen". The claim is that a large discrepancy between the carbon dating of a mummified Ibis and the cloth that it was wrapped in points to the possibility of errors in C14 dating. It is true that the authors did report this discrepancy but they went on to explain possible explanations for the error including the possibility that the Ibis in question had eaten food sources that had higher than normal old carbon ratios. This would be true if the Ibis had eaten from marine food sources or apparently some snails that live in fresh water. The authors didn't think that these possibilities were likely but they thought that additional testing was necessary to determine the cause of the discrepancy. They mentioned that they were pursuing this testing and they ended the paper with this comment:
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 than its 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.
Clearly listing the results of this study without the cautionary information supplied by the authors bordered on intellectually dishonest. Not following up to see what the results of further study by these authors on this issue demonstrated that the authors of the list were not trying to thoroughly investigate possible support for their claim that the C14 testing was unreliable. Perhaps more importantly they didn't mention that the control samples used in the shroud C14 testing included cloth samples of known age that the C14 testing were able to date reliably. They also didn't make note of the fact that even the discrepancy found by the authors of the study was less than half of the discrepancy necessary to explain the size of a C14 error that would be required if the shroud actually dated from early in the first century. And finally the author of the list did not include the estimate of the ratio of the mass of the bioplastic coating to actual cloth that would be required to cause a C14 error that would erroneously have found the shroud to be date from the 13th century instead of the first. From the paper that entry 32 referenced:
For example, if the organic contamination occurred as a result of the 1532 fire and if the shroud really dated to the first century, 79% of the carbon in the linen would have had to come from the fire and thus dated to the year 1532 and only 21% from the shroud itself for the combination to produce the historic date of 1357 AD.
The bottom line here is that what I found when I looked at an entry in the list is a cherry picked, intellectually dishonest summary of a scientific paper. If the list consisted of 31 other entries like this then it does not offer any probative value as to the reliability of the C14 testing. It is just the kind of slanted, non-object analysis that true believers can produce on any issue.
ETA:
(both the items linked to below have been linked to before. I put the links here for the benefit of any people just joining the discusssion)
Link to a discussion between Roger Sparks and William Meacham on the shroud C14 testing
http://www.shroud.com/c14debat.htm
Link to a summary of the shroud C14 test results
http://www.shroud.com/nature.htm