Platinum | Blue Ink Cartridges | 2-Pack for Preppy & Plaisir

The refill that keeps the Preppy going. Your pen came with one black cartridge, and sooner or later it runs dry — usually mid-sentence, usually when you need it. This is the two-pack that means it doesn't stay dry.

There's a small stainless steel ball inside each cartridge, and it's the part that matters. It seals the ink in until you push the cartridge home against the back of the section. After that it stays in there doing a second job: metering the flow so the pen starts clean instead of dribbling the first line, and re-priming the ink when you give the barrel a shake. It's a fussy little piece of engineering in service of never thinking about it.

Paired with the Preppy's Slip & Seal cap, a cartridge left in a pen through a quiet month is still ready when you come back to it in the drawer. That combination — sealed cap, sealed cartridge — is most of the reason a $10 pen has the reputation it does.

Two things worth knowing before you order. Platinum uses its own cartridge size, so standard international cartridges won't fit your Preppy, and these won't fit anything that isn't a Platinum. And this is a dye-based black: deep, smooth, completely legible, but it will run if the page gets wet. If you want a black that survives a damp thumb, that's what a converter and a bottle are for.

SPN-100A #01. Made in Japan. Two cartridges, and the pen is back in service.

• Sealed steel ball — holds the ink until you seat the cartridge, then meters flow and re-primes the feed when you shake the pen
• Fits Platinum Preppy, Prefounte, and Plaisir — every nib size and barrel color
• Works in Platinum sign pens too — the same cartridge feeds the marker-nib pens, not just the fountain pens
• Roughly 1 ml per cartridge, two per pack — a straightforward reorder rather than a project
• Dye-based black — rich, smooth, and fast to start; not water resistant
• Platinum proprietary fitting — does not accept or replace standard international cartridges, so plan your refills around it
• Prefer bottled ink? — the same pens take a Platinum converter, which opens them up to Mintvalley Daily Ink
• SPN-100A #01, made in Japan — Platinum's own cartridge, not a third-party fill