How To Solve Pen Leak Problem

Ink leaks are the biggest enemy that interferes with comfortable writing, aren’t they? No matter how many times you wipe off the ink with a tissue, the day your hands are immediately stained with ink again, you’ll feel like you’re going crazy. So let’s take a look at some of the main causes of the pen leak problem and what you can do about them.

Please note that this article deals with ink leaks from ballpoint, gel, and rollerball pens. So for fountain pen ink leaking, please refer to “How To Solve Fountain Pen Leaking Problem”.

Why Does Pen Ink Leak?

When you hear about ink leaks from writing instruments, the first thing that comes to mind is probably fountain pens. The fact that you have to put ink by yourself gives it that image. However, ballpoint pens also have the possibility to leak ink.

Air gets inside the refill

If you look closely at the tip of a ballpoint pen, you will see a small ball attached to it. Usually, this would act as a lid so that the ink from the pen does not leak out. However, there are times when air gets trapped in the pen tip. And if that happens, the ink will not come out properly, and the writing will be blurred.

If you continue to use the ballpoint pen in this condition, the air inside the refill will increase rapidly. As a result, the ink flows backwards and leaks out.

Why does the ink flow backwards and pop out? It’s hard to visualize “air entering the pen tip” and “ink flowing backwards and leaking”. To make it simpler, let’s use the analogy of a glass of water and a straw.

A straw on a plastic cup filled with ice coffee

If you put a straw into a glass of water, cover the straw’s mouth with your finger and lift it up, the water in the straw will be held without falling down. But, once you remove your finger from the straw, the water will flow down at once. I assume everyone has tried this at least once in a cafe. And this is the same principle as the leakage of ink from a pen.

The most common cause of air getting into the refill is “upward use”. It doesn’t have to be straight up, but air can quickly enter if the angle is above the horizontal.

Therefore, if you have a habit of writing on a wall calendar or taking notes without using a desk, you are more likely to experience ink leakage.

Water-absorbent material touches the tip

Most pens are designed to emit ink when the nib touches something. So, if the pen touches a spongy tissue or cloth, the ink will come out rapidly. That is due to this phenomenon.

Suppose you throw a ballpoint pen into your bag with the nib uncapped and exposed. Since the ballpoint pen is lying down in the bag and the nib is sticking out, the nib may touch the bag and unintentionally let air in through the nib, which may lead to ink leakage.

Broken nib

The pen nib has a very delicate structure with a fine ball assembled on the end of a thin metal pipe. So, even poking an object with the nib or dropping it on the floor can damage it. And in some cases, the nib may become deformed, resulting in thicker strokes or ink leakage.

Also, if you write with the pen lying down too much, the parts that hold the ball will wear down on the paper. And the stroke may become thicker, or the ink may leak out, just like when the nib is damaged.

Impact (e.g. Gel ink pen)

pen refills on a white table

Usually, a pen has an ink follower (a gel-like liquid that moves to the nib side as ink is consumed), preventing air from entering the refill.

However, if the pen receives a strong impact, a tiny hole may appear in the follower. And it will make the ink follower unable to function properly. If the nib is left tilted more than horizontally in this condition, air may enter the nib, and ink may flow out of the back of the pen.

If it is leaking from the back of the pen instead of the nib, suspect a broken follower.

High temperature

Imagine you left a pen at a high temperature for a long time, such as in your car in summer. Under that condition, the air in the ink or follower may expand and push the ink or follower out of the back of the pen.

Please check the storage environment if the ink is leaking from the back even though it didn’t have any strong impact.

How To Prevent Pen Leak

ballpoint pen on a blank white paper

Rething storage condition

If you put pens in a pen case or box, they may end up facing sideways or upwards. If you leave it in this state for a long time, air may enter the refill. So, it’s recommended to keep the pen in a pen holder with the nib facing down.

Use a pen suitable for writing upward

If you can’t change the way you store your pen, or if you often write at an angle above the horizontal, choose a pressurized pen that allows you to write in an upward position.

Pressurized pens have a sealed ink tank in the refill so that you can write in any direction. Various manufacturers sell pressurized pens, so check them out if interested.

Uni Power Tank
Tombow Airpress

Avoid using oil-based pens

Oil-based ballpoint pen ink is more viscous than water-based ink and tends to accumulate in the nib as you use it. This is especially true when the ball of the nib is moving in the same direction all the time.

If you find that your sleeves often get dirty when you write with an oil-based ballpoint pen, you may want to switch to a water-based pen. It’s important to understand the characteristics of each type of pen ink and choose the one that suits you best.

When Your Clothes Got Ink Stains

If your clothes are stained by leaking ink, do not rush to scrub them with soap. This may spread the ink and end up having the opposite effect. For ink stain problems, please check “How To Remove Pen Ink From Clothes”.


Those are the brief ideas of the mechanism of how ink leaks from pens.

Since most ink leaks occur when writing upwards, the first thing to do is to avoid writing with the nib pointing upwards.

Some people have to write on a piece of paper taped to the wall, or they often write memos standing up due to their work. For those people, I recommend trying a pen that allows upward writing.


One thought on “How To Solve Pen Leak Problem

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