Sailors Pigmented inks are permanent and water-resistant, so theyre great for important letters and documents. Seiboku is a bright blue color. Pigmented inks contain tiny particles which can clog up a pen if it sits for too long without writing, so its best to clean your pen regularly when using them.Staff pick!Jean says: These permanent and strongly water-resistant inks are my favorite when Im writing something that I want to keep. They write smoothly, are easy to maintain compared to most permanent inks, and rarely bleed or feather, even on copy paper.Pigment-based fountain pen inkAvailable in 50 ml bottle or 4 ml sampleLooking for a different shade of ink? Ourinkcomparisonchartshows all the colorsside-by-side.