23-04-2026, 06:58 PM
(This post was last modified: 23-04-2026, 06:58 PM by Jorge_Stolfi.)
(23-04-2026, 04:04 PM)eggyk wrote: You are not allowed to view links. Register or Login to view.Do you have source for those UV images of f17r? Are the full pages, or other pages, available somewhere? I would really appreciate them if possible!
Sorry, I did not manage to reply before the other thread was locked. Lisa made the scans available on Google Drive some months ago:
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Only 10 of the pages were scanned. For 8 of those, I converted the TIFF files to PNG (less than 1/2 the size with no loss of information), rotated them to be upright, and extracted some clips that interested me. (I skipped You are not allowed to view links. Register or Login to view. and f47r; will get to them some day).
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See the file 00-Notebook.txt in that directory for an explanation of the file structure. Note that all images will look black if displayed "as-is" because (like the original TIFFs) they have 16 bits per sample but use only 12 or so. So each image should be scaled by 65535/maxval where the maxval value is given in the file "bands.txt" in each page's folder.
Quote:Now, about the reflectivity/absorption of iron-gall inks, I do wonder if this is influenced by the thickness of the ink, the composition of the ink, and the amount of time the ink has been exposed to the elements. The paper you linked appears to be discussing iron-gall ink that is hidden under paint, and is thus not exposed to the atmosphere. Ink that may have oxidised/reacted over centuries may have different absorptive properties to "fresh" iron-gall ink.
The thickness is sufficient for the ink to look dark brown under visible light, so it should be thick enough to look dark also under IR, if the material did absorb IR.
The effect definitely depend on the composition of the ink, and that is the point. But if it were IGI, there is not much room for variation in the composition.
Maybe the the ink was IGI but the tannin has degraded and left behind only the iron as iron oxide. I don't know if that can happen. (I think that IGI is indigest even to fungi.) But that would have made the ink damageable by water or rubbing, as if it were watercolor ink. Considering what we can see on f116r, the ink was "not IGI" already centuries ago.
All the best, --stolfi