Hi Elaine,
I started off with the Rotring Variants, which came in decimal point sizes, and the ones I used most often were 0.1 mm and 0.2 mm, occasionally 0.3 mm, 0.5 mm, 0.7 mm and 0.8 mm. These you did fill with "drawing ink", and I had black, yellow and red (the only colours available).
Because they were so expensive (for a student anyway) and did block up, or wear fairly quickly, I tried out Faber Castell drawing pens once. That was a real waste of money. They never wrote well and blocked even more easily.
Next they came out with the RapidoGraphs, and they came in exponential sizes, as I call them, the smallest being 0.13 mm, next 0.18 mm, 0.25 mm, 0.35 mm, 0.5 mm etc. These are the ones that came with cartridges of ink, which I happily refilled of course. I didn't know about the drop of water trick, but I can assure you, despite having inner caps, unlike the Variants, they still do dry out, especially the finer pointed ones.
I realize stylographs are different pens, but the principle is the same, as far as I understand, with the little weighted needle within a hollow tube. I did repair many of these drawing or architectural pens in the period I used them a lot; I even routinely fixed the 0.1 and 0.13 mm ones, taking them apart, and getting the weighted needles back into the little tubes again without bending them. O, how patient I used to be

.
Nowadays I use a fine nibbed fountain pen for very fien writing, but occasionally it is just too wide. I should actually see what the result is with fountain pen ink in these, hmmm, new little project

. I still have a Variant 0.1 mm in working order, and several RapidoGraphs. Ok, new little project... As if I don't have enough little projects already

.
Anyway, quite a long post considerign my original intention: I saw Denis' remark about the bunnies being in sync, played with them, and just looked for a post by Karin to reply to and add the bunnies, without being too much OT

. I hope you'll forgive me for that...
So, one more time, dancing bunnies

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Warm regards,
Wim