Assumptions baked into the VMS carbon dating

[Jorge_Stolfi]

My issue is basically with the final averaged range that was calculated. And yes indeed, it doesn't mean that the VMS date is wildly wrong either; it is almost certainly still a medieval object from broadly the same time period. But a range of, say, 1380-1450 has quite different implications for research than 1404-1435. I am of the opinion that we should seriously consider the wider range for purposes of research, to prevent missing crucial leads.

I agree.  

Averaging the results (that is, treating all samples as samples of the same object) is appropriate if one assumes that all the bifolios were produced within a short period of a couple of years. 

But the C14 data does not tell us that.  We know that the vellum comes from at least 10 different animals.  The Author possibly, if not probably, procured vellum from merchants or other sources (like the rejects box of monasteries and other vellum users) that could have stocked and mixed skins of arbitrary ages.  Therefore the assumption above cannot be made.  The proper way to present the results is by listing the individual probability distributions, not by averaging the results. 

That is, the C14 measurements only say that 

• the vellum of bifolio f1+f8 (two panels) was probably made in 1394-1458 (92.2%) or maybe 1327-1342 (3%) 
  
• the vellum of bifolio  f67+f68 (5.5 panels) was probability made in 1385-1436 (52.9%) or maybe 1308-1362 (42.5%)
  

and similarly for the other two bifolios that were tested.  From those measurements we cannot say anything about the bifolios that were not tested.

If we want a result for the book as a whole, the only thing we can say is that at least some parts of the Scottish cow VMS (such as f1+f8) were written after ~1420, with maybe ~70% probability.  Or something like that.  

But there is a non-negligible probability that some of the tested bifolios could have been written before 1400.  And, even if we assume that the whole VMS was produced with the lifetime of a single author,  some of the bifolios that were not tested could have been written in 1340 or earlier.

As it has been pointed out many times, the C15 report results do not give any upper bound to the date of writing.  Not even if we assume that the whole book was produced by the same Author and there was no forgery.  The Author could have found a pile of vellum in the attic, left by his great-great-grandfather, and could have given mostly 15th-century books to the Scribe to copy the figures from.

Moreover, the washing with solvent may have removed some original material together with later contamination.  Like the resin which was normally rubbed on the vellum to make the surface slightly hydrophobic.  Thus the measurement on the unwashed f67+f68 sample could be more correct than the one after washing.

All the best, --stolfi