The Book Switch Theory

[eggyk]

But that slide is misleading.  I have now seen the actual calibration dates.  It turns out that, because of a geophysical hiccup around 1400, the measurement of each sample yielded two separate estimates, each with its own range and probability:

f8    1334± 7  3%   1426±32 92%

f26   1335±14 12%   1419±28 83%

f47   1334±10  7%   1420±28 88%

f68   1335±27 42%   1410±25 52%

Folio 8: 490±37, which works out to 1423 to 1497
Folio 26: 514±35, which works out to 1401 to 1471
Folio 47: 506±35, which works out to 1409 to 1479
Folio 68 (cleaned): 550±35, which works out to 1365 to 1435

I will say that although folio 68 has "cleaned" next to it, all of the folios there were "cleaned" the same way. It was only to differentiate it from the uncleaned version of folio 68, which isn't included in that list.

All of this can be found at a link at Rene's site, which has the published figures and graphs that are being mentioned here (including the dual peaks). 

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If we assume that all four folios came from the same batch, the date for that batch is about 1420±25 with 90% probability (sorry, rough math here -- too tired now do the proper computation).  But 

If we assume that the folios may have come from different batches, like scavenged from old books or from various "reject" bins, there is ~50% probability that folio f68 was made in 1335±30, while the other three were made around 1420; and ~50% probability that all four folios were made around 1420.  In both cases, the dates around 1420 could possibly be 10 years apart or more.

Exactly. 

The merging/averaging of the different C14 results by treating the different folios as "a single object measured 4 times" is, in my opinion, nonsense. They are different pieces of parchment, and could very well have been created decades apart from eachother. Especially if the low quality of the parchment represents an author using the parchment from their waste/extra parchment stores.  

The fact that these averaged results are taken as irrefutable fact is troubling. We do not have a 95% probability of a date between 1404 and 1438, we have a 95% probability of a date between 1404 and 1438 assuming that each folio was part of the same object. 

It would be more accurate to say that each piece of parchment tested so far was likely created somewhere between 1365AD-1497AD.