Yes, I am well aware of the changes in darkness due to mere variations of ink flow. Like suddenly darker after dipping the pen in ink, then gradually lighter as the pen runs out of ink. Or when the Scribe him/herself goes back and corrects some mistakes. Or when he/she presumably mixes a new batch of ink halfway through a page. But those are easy to spot because (1) the
hue of the ink does not change, and (2) the sequence makes sense considering the way he/she must have operated.
And I am well aware of the chemistry of iron-gall ink.
However, the retracings by the Retracer are quite distinctive in both counts. The ink is not just darker, but has a different hue and appearance: almost black, tending to purple rather than yellow -- as one would expect from iron-gall ink. And it is applied in an unsystematic manner: either on parts (text
or figures) where the original ink had clearly faded with time, or to add details that clearly were not there initially, like the crowns and "lobed showercaps" in the Zodiac pages.
Of the images you posted, You are not allowed to view links.
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Login to view. and the starred parags section are examples of the former. Whereas You are not allowed to view links.
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Login to view. clearly shows the difference between normal ink flow effects (e.g. in the text rings) and the Retoucher's work. The former can be seen, for instance, in the middle text ring at about 02:00: note how the traces become gradually fainter, then suddenly darker but
with the same yellowish brown hue.
In contrast, note how the darker labels are uniformly dark, while the lighter ones, by comparison, are uniformly light apart from normal ink-flow variations. On higher resolution images, as one can download from the Beinecke site, original faint yellowish brown strokes can be seen in places under the dark labels; for instance, the "feet" of the
k gallows on the okedal label in the outer-band at 07:00.
On the figures, note how the darker strokes cannot be explained by ink flow variations or the original Scribe going back to fix mistakes and accidental faint strokes. The darker ink was applied to the right breast of almost every nymph, and to the left breasts, nipples, eyes, eyebrows, and other details of some of them, apparently at random. Check the left thigh of the outer nymph at 05:30, the right thigh of the one at 07:30, and the right arm of the inner nymph at 11:00. All three are (wrongly) retraced over a light yellowish brown trace, which the Retracer apparently did not notice. And the dark traces on hair and "showercaps" of some nymphs are clearly spurious additions.
It would be very helpful if Beinecke provided some really high resolution images, even if only of small selected areas of selected pages. High enough that one could see whether glyphs or figure details have been traced once or twice.
PS - don't waste time and space downloading the "full size original (tiff)" images from the Beinecke site. They are the same as the "Full size (jpg)" images, merely converted to the much more wasteful TIFF format. With the same resolution and JPEG encoding artifacts.