The magic behind a fountain pen’s smooth lines lies in a dance between gravity and capillary action. Here’s the breakdown:

1. Reservoir and Feed:

• Your pen stores ink in a reservoir. This can be a cartridge, a converter (convertible cartridge holding bottled ink), or a built-in piston/vacuum mechanism.
• The feed is a plastic or ebonite channel connecting the reservoir to the nib. It regulates ink flow and prevents messy leaks.

2. Nib and Capillary Action:

• The nib is the metal tip where the ink meets the paper. It has a slit running down the middle and often tines at the tip.
• Capillary action kicks in here. Imagine tiny canals within the nib and feed. Ink, being attracted to itself, climbs these canals due to surface tension.

3. Gravity and Writing:

• As you write, the nib touches the paper, creating a slight vacuum effect. This pulls ink down the feed and onto the paper through the slit in the nib.
• Gravity assists this flow, ensuring a steady supply of ink without needing excessive pressure.

Bonus:

• Air channels: The feed also has air channels to allow air into the reservoir as the ink leaves. This prevents a vacuum from forming and stopping the ink flow.
• Nib variations: Different nib sizes (fine, medium, broad) and flexibility (flex nibs) affect line width and writing experience.