Ink/pen dynamics and the rhythms of writing

[pfeaster]

I've cropped a few locations from UB007 MSI (gamma 1.0, black point at 50% since most of the pen strokes are almost white) and from 2014 visible light scans, TIFF versions, trying to keep the scale. To me it looks like the empty space in the downward flourishes of 'y' and 'm' probably has something to do with the tip of the pen, as you wrote. I'm not sure about 'o', to me it looks like this could be either way (stroke overlap or split tip). I'd say 'r' looks more like a retrace. In the tip of the flower both lines are very sharp and clean, to me this looks more like two separate pen strokes, but this is just my intuition that a split tip trace should look a bit messy with no clear point of departure and convergence between two lines, and not symmetrical on both sides as it is in this case.

I found some sets of instructions for how to prepare a quill pen from a source feather, and I think I have a better sense now for the mechanics of ink and pen that probably underlie what we're seeing.

You are not allowed to view links. Register or Login to view.
You are not allowed to view links. Register or Login to view.
You are not allowed to view links. Register or Login to view.

The tip of the quill has a slit or channel to hold ink, and the original tip has also been shorn off flat to produce a nib similar to that found on "modern" flat-tip calligraphy pens.  The flat tip will produce a line of varying width, with the distribution of thicker and thinner widths varying depending on the nib angle and the direction of pen movement.

In a pen of this design, pressing down on the tip could -- I think -- cause the two "halves" of the tip to separate along the ink channel, and then to "close up" again when the pressure was lifted.  But this would probably occur only with a mildly defective pen.

The instructions at oylmiller.com contain a nice example of a "pen test" with split-nib doubled lines (even used artistically to create a plant drawing!) and variations in darkness (more ink = darker; less ink = paler).

When judging whether pairs of lines are doubled due to a split nib or drawn separately, I'd suggest we consider two criteria: (1) whether the doubling occurs on a stroke where the nib angle should have produced a line at or near maximum width, moving perpendicularly to the flat edge; and (2) how strictly parallel the lines are.

As to f17r: Looking more closely at the [r] in [dor], I now suspect it does contain a "retrace" (downward-rightward, then upward-leftward) but with a gap from a split nib even so.  The overall width of the "\" at the base of the [r] is greater than could have been drawn with a single stroke.  But the thin parallel line along the lower left should have been drawn with the nib angle in position to draw a line at maximum width -- i.e., the pen should not have been physically able to draw a thin line there without being rotated between strokes, but it could have drawn two parallel lines due to a nib split, with the upper / rightward "half" of the stroke overlapping part of the initial downward stroke, leaving only the downward / leftward "half" visible.  Meanwhile, with the [o], the two lines at the top coincide with the greatest stroke width, where doubling due to a split nib would be expected, but an independently drawn thin line would not.  I'll see if I can get my hands on a calligraphy pen so I can draw some illustrations (and try some experiments).