Graf von Faber-Castell Cobalt Blue is a bright blue ink. It is a part of Document Proof series. It means that the ink is resistant to UV light and cannot be altered or removed from the paper without a trace. It was also designed with the standard office copy paper in mind. It doesn’t “feathers” on such paper, and doesn’t bleeds to the other side of the page. It could be used for signing and annotating documents in the common office environment.
Cobalt Blue is suitable for all fountain pens. This ink has a good flow and can be cleaned out of the pen without a lot of work.
Graf von Faber-Castell ink cartridges are Standard International Short cartridges. They can be used in all compatible fountain pens including Standard International compatible pens of other brands. Each cartridge is 38 mm long (1.5”) and contains about 0.8 ml of ink.