Look a little closer
See the mechanism
Ink out, air in
Read the diagram
Feed and split nib. A narrow liquid route connects the reservoir to the conventional nib slit. Air can return to the reservoir through the feed.
Liquid and air paths are simplified and separated for clarity; detailed channels vary by pen.
Diagram basis: Pelikan ink-duct and pressure-regulation explanation.
Sources: Pelikan · William I. Ferris / US Patent Office via Google Patents
The feed connects storage to the point
The metal nib is the visible writing part, but the feed beneath it connects that part to the ink reservoir. A narrow groove or channel carries ink forward. The slit in a conventional split nib continues the liquid path toward the writing point.
When the point touches absorbent paper, ink transfers into the page. More liquid can then advance through the connected wet passages. This differs from a ballpoint pen, whose rotating ball transfers ink at the contact.
Sources: Pelikan · William I. Ferris / US Patent Office via Google Patents
A second route admits air
As ink leaves the reservoir, the space it occupied must be replaced. The feed permits air to enter while restricting liquid flow. If replacement air could never enter, the pressure difference would eventually oppose further ink leaving.
Making an unrestricted opening would create another problem: ink could escape too freely. Feed geometry balances capillary retention, liquid supply and pressure equalization rather than simply leaving the reservoir open.
Sources: Pelikan · William I. Ferris / US Patent Office via Google Patents
The filling system is a separate choice
A cartridge, converter or piston reservoir can store the ink. That choice changes how the pen is filled, but a conventional pen still needs the feed and nib to deliver a controlled amount to the writing point.
Sources: Pelikan · William I. Ferris / US Patent Office via Google Patents
The thing to remember
A fountain pen supplies two linked flows: ink toward the paper and air back into the space it leaves.
What this example leaves out
This is a conventional split-nib explanation. Channel layouts, air-return paths and pressure-control features vary between designs.
Sources & further reading
Source access dates are listed below. Manufacturer descriptions and patents support the specific constructions described, not every product.
- FAQ — How does the ink duct function? ↗
Pelikan · Retrieved 2026-10-18 · Feed/ink duct pressure regulation and capillary restraint; nib, reservoir and filling-system parts.
Read Fine writing instruments, parts/ink duct/filling systems; web lines 253–266. Current manufacturer explanation, not universal channel geometry. - US706140A — Fountain-pen ↗
William I. Ferris / US Patent Office via Google Patents · Retrieved 2026-10-18 · Capillary ink route to nib and entrance of air to replace withdrawn ink.
Read description background and intended balance of forces, web lines 160–169 and definitions 73–79. Historical design evidence only; no priority or adoption claims.
