DeAtramentis's Document White Ink. No clue what science magic happened to make this not clog the hell out of pens... But it dosen't. It has a permanent home in a smaller FPR with an ultraflex nib. This is an always-inked ink. I use a lot of fun high end letterpress papers, and being able to use the dark colored ones is glorious. Def. needs lots of shaking, and takes a bit to get it flowing after sitting for a day or two. But joyous wonderful ink.