Inktend / Pen library / Fission
Nemosine
Fission
A model in Nemosine's fountain pen lineup. Specs below reflect the typical configuration across Nemosine's core range.
A solid mid-range option once someone has decided fountain pens are a habit worth investing a bit more into.
Specs
About Nemosine
Nemosine was an American value-oriented fountain pen brand best known for the affordable Singularity and Fission models with interchangeable nibs. The brand was wound down at the end of 2019 when its owners shifted to US-made pens and inks, and it was effectively rolled into the Birmingham Pen Company.
How to fill the Nemosine Fission
Fill it two ways: snap in a pre-filled international cartridge for convenience, or use a converter — a small plunger or twist mechanism that installs the same way a cartridge does — to draw ink from any bottle. The converter route opens up the entire world of bottled ink, which is where most of the hobby's color variety lives.
Choosing a nib size
Nib size determines line width, not writing pressure — fountain pens are meant to glide, never press. Extra-fine (EF) suits small, dense handwriting and thin paper; fine (F) is the most broadly recommended default; medium (M) shows more ink character and shading; broad (B) and stub grinds favor bold, expressive strokes and calligraphy-adjacent writing.
Keeping it clean
A quick flush with cool water every time you switch ink colors — and a full clean every 4–6 weeks of regular use — is enough to keep the nib and feed performing well. Inktend's cleaning reminder is tuned to a 21-day baseline and adjusts naturally to how often you actually refill.
Pairing inks with the Fission
Because refills are quick with a cartridge or converter, this is a good pen for rotating through several colors rather than committing to one; sample vials work especially well here.
Frequently asked questions
More from Nemosine
Specs reflect the typical configuration across Nemosine's core lineup rather than this exact model — check current listings before buying.