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Why Do Pens Explode? – 3 Main Causes & How to Prevent

Written by Robert S. Brown / Fact checked by Helen B. Harris

why do pens explode

Are you often finding yourself with ink-stained pockets or smudged documents? One of the common yet baffling issues that many people encounter is when pens explode or leak unexpectedly.

Why do pens explode? This can happen due to temperature changes. Leaving a pen in a hot environment, such as under direct sunlight or high heat, can result in the ink’s volume expanding, creating internal pressure that can lead to an ‘explosion’.

This article will delve into how do pens explode, outlining the common causes and warning signs of imminent pen shattering. So, keep reading to know more!

Common Causes of Pen Explosions

It’s annoying when seeing your pen running out of ink due to leaking. In fact, pens can explode for various reasons, including overheating, air pressure, and poor-quality pen tips.

1. Extreme Temperature Changes


This is the most common reason for an exploding ink pen. When a pen is exposed to excessive heat, such as being left out in the sun, near a heat source like an oven, the ink inside the pen can undergo a process called thermal expansion.

For example, you can find a pen leaking in pockets. This is because our bodies generate warmth, and when you put a pen in your trousers, it will get hot. With nowhere else to go, the ink is forced out of the pen, either gradually creating a leak or causing a sudden rupture or “explosion” of ink.

Something similar happens when you put your writing tool in a freezer or travel in very cold weather. The ink expands as temperatures plummet and leaks out once it gets warm.

2. Air Pressure


In normal conditions, the pressure inside the pen balances with the outside environment. When the external pressure drops suddenly and the pressure inside the pen becomes significantly higher in comparison, the ink can leak out. This occurrence is common during flights.

3. Damaged Pen Tip


Damage to the pen tip can also result in a pen exploding or leaking. The pen tip, or nib, serves as a controlled gateway for ink flow from the reservoir to the paper. If the nib gets damaged, bent, or fractured, it can disrupt this controlled flow.

Rather than the ink being channeled out in a controlled manner as you write, the ink can freely flow or even spurt out, giving the effect of the pen exploding.

In more severe cases, the damage might cause a real rupture in the pen reservoir, especially if the pen is squeezed or experiences further physical stress. This could lead to a significant ink leakage.

Accidental Rubbing

This reason is probably the simplest one. If you forgot to retract your pen or there’s friction between the pen tip and the pocket as you move, ink can leak out and cause an ‘explosion’.

How Do I Know if a Pen is About to Explode?


Determining if a pen is about to explode can be challenging, as there are often no clear warnings before it happens. However, if you find your pen having the below issues, you should check it or just stop using it for a while. Here are some indicators:

  • Small amounts of ink around the nib or inside the cap
  • The ink is coming out more freely than usual.
  • Physical damage to the pen, like cracks, bends, or a damaged nib.
  • If your pen has been in a hot/freezing environment or experienced significant pressure changes.

How to Prevent?


Here are some tips to prevent a pen from exploding:

  • Avoid Heat: Keep your pens out of direct sunlight and hot environments like in the pocket or on a car dashboard.
  • Store Properly: Store your pens upright with the tip facing up in a cool environment. It’s best to keep your pens with the cap on.
  • Be Mindful of Pressure Changes: Be cautious when traveling with pens, especially by air. If flying, consider using leak proof ballpoint pen like Bic pens. You also can keep your pens in the carry-on or their own sleeve, which is less susceptible to pressure changes.
  • Regular Maintenance: Clean your pens regularly, especially fountain pens. This helps keep the ink flowing properly and can prevent clogging that might lead to a leaky fountain pen.

Frequently Asked Questions

Are Some Pens More Prone to Explosion Than Others?

Yes, old fountain pens, rollerball pens, and ballpoint pens are more likely to explode than others.

Fountain pens leak mostly due to their liquid-ink systems, which are sensitive to external factors. Environmental heat can cause air expansion inside the pen, thereby forcing the ink out. Even the warmth of your hand may trigger this phenomenon.

Otherwise, fboth ballpoint and rollerball pens have the ball at the pen tip that controls the ink flow.

When the ink inside the pen becomes overly liquefied due to high temperatures, the ball might become insufficient, which can make ballpoint pens explode.

Are There Any Pens That Won’t Explode?

Although it’s hard to find the best no leak pens, some varieties present a lower risk of leaking, including new design fountain pens and gel pens.

It may sound confusing, as the previous answer said fountain pens are more likely to leak. But it’s only true with the old models. Modern fountain pens have been refined over time to mitigate the chance of ink leakage or explosions.

Gel pens also pose a smaller risk of exploding due to their thicker ink, delaying liquefaction even when subject to high temperatures. Nevertheless, under prolonged exposure to heat, gel pen leaking is completely possible. So, to stop a gel pen from leaking, it’s crucial to store them carefully.

How to Clean Up Ink Spills

Cleaning up ink spills can be easier if you take immediate action.

  • Firstly, use a dry cloth or paper towel to blot the excess ink gently.
  • Next, treat the stain with a mild soap and warm water solution. Apply the soapy water onto the stain, and gently blot using a clean cloth. Repeat this process until the stain fades.
  • For stubborn stains, you can apply a small amount of rubbing alcohol or stain remover.
  • Finally, wash or clean the area as usual to remove any residual soap or cleaner.

What to Do if a Pen Explodes?

When ink come out of pens, follow this step-by-step guide!

  • Ensure the cartridge and converter are installed correctly and intact. Place the nip upward to stop pen from leaking and causing further damage.
  • Use a paper towel to blot the ink spilled.
  • Apply an appropriate cleaner or alcohol to the stain and the pen cap. If the stain on fabric, you might use alcohol. For hard surfaces, dish soap mixed with warm water works well.
  • If the stain is on a washable material, rinse it under cold water. If it’s on a hard surface, use a wet cloth to wipe off the cleaner.
  • Wash or Clean as Usual to remove any remaining residue.


This is the end of our article on “Why do pens explode?” Pens explode mostly due to changes in pressure, exposure to extreme temperatures, and damage to the pen tip. These triggers cause the ink to leak out violently, creating what we perceive as an ‘explosion.’

Understanding these factors helps us mitigate the risks. By keeping pens at moderate temperatures and storing them carefully, you can significantly reduce the chances of pen explosions.

Ultimately, prevention and swift response to ink spills are our best defenses against the messy aftermath of an exploding pen.

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