Physics Pulse x Fluorescent Mag Collab

Ever wonder how mundane objects like fountain pens work?

By: Fluorescent Mag

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Introduction

Ever wondered how mundane objects like fountain pens work? 

Turns out, there's a lot of interesting physics involved!

Fountain pens use a combination of capillary action and surface tension to draw ink from the reservoir to the nib, allowing for smooth writing.

Capillary Action

Definition: The ability of liquid to flow in narrow spaces without external forces. This occurs due to the adhesive forces between the liquid and the surface of the material.

How It Works:

• In a fountain pen, ink rises through the feed, which has narrow channels.

• The ink molecules stick to the walls of the feed (adhesion) while also pulling along other ink molecules (cohesion).

• This combination creates a continuous upward movement of ink, ensuring it reaches the nib efficiently.

  
  

Another example of a capillary action is drinking through a straw. When you sip through a straw, the liquid rises inside due to capillary action, moving up the narrow straw against gravity.

Surface Tension

Definition: The cohesive force at the surface of a liquid, causing it to behave like a stretched elastic membrane and have the least surface area possible.

How It Works:

• Surface tension helps keep the ink in the nib and feed, forming a stable reservoir until you start to write.

• When you apply pressure while writing, the force exceeds the surface tension, allowing the ink to flow smoothly onto the paper.

• This ensures a consistent ink delivery for a satisfying writing experience.

Another example of surface tension is soap bubbles. Soap reduces water's surface tension, allowing the bubbles to expand and maintain their shape while containing air.

Ink Delivery Mechanism

Nib Design: The nib of a fountain pen is uniquely shaped with a slit that controls the flow of ink, based on pressure and speed.

Pressure Application:

• When you press the nib against paper, you create a small gap in the slit. This gap allows the ink to flow out due to the pressure and the combined effects of capillary action and surface tension.

• The ink is drawn down from the feed to the nib, filling the gap created by the pressure of writing.

Continuous Flow:

• As you write, the nib continuously replenishes itself with ink due to the capillary channels within the feed. This ensures that the nib remains wet for consistency. 

• The balance between the ink’s viscosity (thickness) and the nib’s design is essential, as an ink that's too thick can clog the nib, while too thin can lead to excessive flow.