Uni Posca 0.7mm White Marker
Write on wood, glass, metal, plastic, ceramic, leather, and more.
For permanent markers, Sharpies are a beloved and widespread choice. For non-permanent markers, the Uni Posca line is my go-to choice. They are water-based, non-toxic, dilutable (they do smudge if not careful) markers which can write on pretty much any surface. And the main one I use is a white, 0.7mm one, though they are available in a bunch of colors and tip sizes and styles, from fine liner-style, to brush tips, to huge square ones.
I 3D-print a lot of things and especially for test prints or functional parts I often default to either silver or black filament. With the fine tip I can write on small parts and surfaces without problems, white contrasts excellently against the black prints, the ink coverage is pretty good and it flows well. The only downsides I‘ve noticed are that the ink dries a tad slowly, and I occasionally need to shake and pump the pen to continue writing.
Because it‘s water-soluble it‘s also fairly easy to accidentally smudge the ink, so do be aware of that. On the other hand, it‘s fairly easy to remove because of it. Since getting the marker I‘ve also tried it on other surfaces, including dark wood, dark metal (sharpening angle on blued plane blades), various plastics and whatnot else popped up. It wrote on anything just fine, and unless the material was too rough or porous, I could also remove the ink fairly well just using some water. I‘ve used one marker for over a year now and it‘s still going strong without drying out or any signs of stopping anytime soon.03/10/21