I've recently joined a special interest group on facebook--a group discussing fountain pens. And I learned something really interesting.
The discussion that caught my interest was someone who'd bought a TWSBI vac-fill was complaining about writing for a few lines, then it drying up and skipping until they'd "primed the pump, so to speak." They got a response that floored me.
Vacuum fill pens are designed that way. If you want to write with them continuously, you have to unscrew the fill knob just a little bit. Otherwise, it seals the ink away from the nib and feed. That fill method was designed for businessmen that flew frequently: it's safe to fly with a fountain pen that's sealed shut.
Cool as hell. I want one, now. Between the massive ink capacity (2.3 mL ink) and the fill method, I want one. Someday.
Oh, and I finally found a pen that likes the Noodler's Bad Belted Kingfisher (water/fraud resistant navy blue ink): my Parker Frontier. Pen and ink work together like a freakin' dream. The ink actually settled the pen down (laid down too much of other inks, but is perfect with this one).
Thank God. I love that color of blue ink, and I have a 90 mL bottle of it.
26 minutes ago