( I'm not sure in which forum subsection this post rightly belongs, when it is:
• not a review of Sailor seiboku pigment ink; and
• not comparing seiboku against any other ink. )
After @crahptacular clued me in (thanks!) that the relatively wide range of colours that I elicited from Sailor souboku is related to the idea of 'dryness' of nibs and inks, and it occurred to me that it is not unlike the phenomenon of shading but elicited using multiple nibs over different lines of writing, I set out to identify the 'standard' ink review equipment I would use to show the variation in appearance of a particular ink that is possible from especially fine nibs, which as a category are my personal preference for writing by hand.
To that end, I tested the bunch of cheap Japanese desk pens I bought recently, after being inspired by LizEF's question, for different degrees of 'wetness' hoping to find two or more that lay down similar line widths but show distinctively different colours from an ink.
Outside of Iroshizuku asa-gao and Diamine Sherwood Green, I have also tested Sailor seiboku, chosen for its kinship with Sailor souboku and the trouble I had with using it in my Sailor Pro Gear with a 21K F nib. These are scans of the results.
I've marked with an asterisk❋ the instances in which I used a nib for dipping only without attaching a converter or cartridge to the feed.
Just like with Sailor souboku, there is quite a range of colours differing by intensity/saturation on the page. Having tested with three different inks, I have found no agreement as to whether using a converter to feed the nib – after suitably draining/drying it with a thirsty paper towel, then attaching the converter to the nib, and use the paper towel again to help draw ink through and prime the nib for writing – results in 'wetter' writing than by dipping the nib.
- With Sailor seiboku (shown above), converter-fed writing is noticeably 'drier' than with a dipped nib, particularly with the three Platinum desk pens; the Sailor and Pilot desk pens were not as significantly affected.
- With Diamine Sherwood Green, converter-fed writing is slightly 'drier' than with a dipped nib, but the differences are not as pronounced.
- With Iroshizuku asa-gao, converter-fed writing is noticeably 'wetter' than with a dipped nib, and I can see it in all of the Sailor and Platinum desk pens tested. (I didn't use a converter with the M-nibbed Pilot to test that.)
At this point I'm inclined to conclude that:
- The Sailor 11-0073-120 desk pen, used with or without a converter attached, is a fit representation of a (moderately) 'wet' EF-nibbed pen.
- The Platinum DPQ-700A with EF nib, when used as a dip pen, writes 'drier' than the Sailor.
- The Platinum DP-1000AN with EF nib, when used as a dip pen, writes even 'drier' than that.
- The Platinum DP-1000AN with F nib, when used as a dip pen, writes significantly 'wetter' (more than merely laying down thicker lines) than the Sailor, judging by the intensity of the colour and relative lack of shading in the writing samples produced with it.
- The Pilot P-DPP-1S-BM with M nib, when used as a dip pen, approximates a slightly 'drier' writer that lays down similar line widths as the F-nibbed Platinum.
By the way, the Sailor 11-0073-120 has the scratchiest nib by a long shot among all my desk pens, and if I manage to get a relatively smooth writing experience with it using a particular ink, I think that would attest to the ink's lubricating capability.