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Prisma

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A model in Radius's fountain pen lineup. Specs below reflect the typical configuration across Radius's core range.

A solid mid-range option once someone has decided fountain pens are a habit worth investing a bit more into.

Specs

Filling systemCartridge / converter (typical for most fountain pens)

Ink capacityVaries by model

Nib optionsF, M (steel, typical)

MaterialResin or metal

Typical priceVaries, check current listings

How long has your Prisma been inked?

Inktend counts the days and reminds you when it's time to clean.

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About Radius

Radius was an Italian fountain pen brand trademarked in 1934 by SAFIS of Turin, whose Superior line was regarded as rivalling the best Italian makers such as OMAS and Aurora before production ended in the late 1950s. The brand was revived in 2019 as Radius 1934, producing Italian-made fountain pens in collections such as Settimo and Superior.

See all Radius products →

How to fill the Radius Prisma

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, plus a full clean every 4 to 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 Prisma

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.

Blue

Koh-i-noor

All that matters - Pigment Black

KWZ

Hehuan Blue

Lennon Tool Bar

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Frequently asked questions

How do I fill the Radius Prisma?

Snap in a pre-filled cartridge, or use a converter to draw ink from any bottle. The converter route is the cheaper long-term option.

What nib size should I get for the Prisma?

Fine (F) is the safest default for a first pen. Go finer for small, dense handwriting; go broader if you want more ink character and shading.

How often does the Prisma need cleaning?

Flush it each time you switch inks, and give it a full clean every 4 to 6 weeks of regular use.

Is the Radius Prisma good for beginners?

It can work as a first pen if you're comfortable spending a bit more to start.

More from Radius

Settimo

Radius

Specs reflect the typical configuration across Radius's core lineup rather than this exact model. Check current listings before buying.