Hair side, flesh side and Gregory's rule in the VMS

[Jorge_Stolfi]

So, I might have been following a Halloween ghost...  Nevertheless, in case it's of interest, this is how and what came out.

I think your research on vellum sides is very interesting, but for me the results are only another bit of evidence that the VMS Scribe was not a professional one.  He may have had some experience with writing with a quill, but had never worked with vellum and had never copied a book

On each square I used the same filter (lightness minus a slightly blurred copy, which keeps detail under about half a millimetre) and took its spread as the grain.

I cannot see the hair pores on the Beinecke images. At least not on the "full resolution" jpegs that I download from their site (or the tiffs, which -- as is often the case with consumer cameras -- are just the jpegs converted to the vastly bigger tiff format).  Here are clips from matching spots of You are not allowed to view links. Register or Login to view. and You are not allowed to view links. Register or Login to view. (as closely matching as I could):
       
One reason for this failure may be that the lighting in those images was nearly perpendicular to the page, which would have lighted up the bottom of the pits as much as the vellum around them.  

But another reason must be that vellum was usually finished by saturating it with with chalk and other substances, precisely to fill the pores and cavities so as to create a better writing surface. 

Still the rough texture is more evident where that obnoxious green "copper resinate" paint was applied on the other side, as seen in the clips above.  I suppose that this effect was the result of the paint soaking into the chalk filler, and/or of those green ghosts being due to light that crossed the vellum twice -- instead of just bouncing off its surface. 

I cannot distinguish the "hair" and "flesh" sides of the vellum on the multi-spectral images either.  Their resolution (pixels/mm) is almost double that of the BL color images, and they are free from JPEG artifacts. However, in that collection there are no images that were taken from the two sides of the same folio, so I could not do a direct comparison there.  Maybe with suitable processing one can reveal the pores on some of the pages.

The McCrone report contains some 19 images of the areas where the samples were collected, with much higher resolution. These are about the extremes in terms of apparent roughness:
       
(Those are images 0026 and 0014 as extracted from the PDF; I cannot check their f-numbers now, sorry.) But i cannot see pores on them either.  Maybe, by sheer bad luck, McCrone took all its samples from the flesh side of the vellum, and the different roughness in the clips above may be due to different degree of polishing, or just different lighting.

Yet I can see the pores very clearly on the vellum of the cover:
   
Could it be that the VMS page vellum does not have visible pores?  Gemini halluc tells me that sheep skin could be prepared in a way that it would have no hair follicles visible, even under a microscope...

All the best, --stolfi