Fountain pen ink
![A 2-imperial-fluid-ounce (57 ml) bottle of Quink brand, fountain pen ink](/Images/godic/202501/14/Parker_Quink_Bottle5153.jpg")
![A blot of Quink ink on damp paper – the blue dye has separated from the other components, which are peach–coloured](/Images/godic/202501/14/Quink_Blot5153.jpg")
![Europen Ink Bottle](/Images/godic/202501/14/Europen_Ink5153.jpg")
![Two Lamy fountain pens, with an ink cartridge and a piston–type converter](/Images/godic/202501/14/LAMY_safari_and_vista_with_a_cartridge_and_a_confertor5153.jpg")
Fountain pen ink is a water-based ink intended for use with fountain pens.
Because fountain pens operate on the principle of capillary action, ink for them is almost exclusively dye-based. Pigment-based inks (which contain solid pigment particles in a liquid suspension) tend to clog the narrow passages of the pens. Some pigmented inks do exist for fountain pens, but these are uncommon. India ink, a carbon pigment-based ink, also contains a binder (such as shellac), which can quickly clog such pens. The ideal fountain pen ink is free-flowing, free of sediment, and non-corrosive. These qualities may be compromised in the interests of permanence, manufacturability, and in order to use some widely available dyes.