Ink/pen dynamics and the rhythms of writing

[pfeaster]

I'm trying to see the doubling on f17r, couldn't find anything in the main text. Could you help me by pointing at some specific locations on the page? There is one 'o' with doubling at the top, but this could be just the start and the end of the stroke overlapping. The only place where I see the doubling clearly is the top of the central flower, and even there I'm not sure whether this looks like a defect of the pen or just a double stroke, since both lines have a very clean edge.

Here are a few cases I had in mind, though some of them are admittedly subtler or more questionable than on the other pages I mentioned:

   

What I'm picturing is a split tip that separated progressively into two halves as more pressure was applied to it.  I'm also making some assumptions about the strokes used to form each glyph -- i.e., [o] typically seems to have been drawn as two strokes (an [e] plus a second oppositely curved stroke), and not as a single circular motion with an overlap.  Higher-resolution images could help disambiguate -- based on the best images I have, I'll concede that the doubled line of the [r] in [dor] could conceivably be a "retrace," although I don't think [r] was ordinarily written that way.  The processed MSI images don't clarify this.  The raw TIFFs might.

Curiously, there is also a little bit of empty space in 7 in the folio number, but this is probably unrelated.

Folio numbers and zodiac month names both show a similar line-doubling, but I agree that they're probably unrelated, except that they might have a similar physical cause.

Update: I've cropped the start of the top margin inscription from UV_007 TIFF from the MSI set, there is no processing here other than cropping and conversion from 16 bit to 8 bit. To me this shape variation in 'a' looks more like a correction than a pen defect, but I'm not an expert in quill writing.

Neither am I, though I've had to study the mechanical behavior of flexible stylus tips for other reasons.  This TIFF makes me start to have doubts, but here's what I was initially comparing, rightly or wrongly: