One of the most painful lessons, a true “hard-earned” experience that we all must go through to grow in life, is the cut from paper.
At some point, we realize that not only knives can cut; even a sheet of paper can slice into our skin. In fact, paper cuts can hurt more than knife cuts.
When was the last time you got a paper cut? Was it when you just pulled a sheet out of the printer at work? When you flipped open a newspaper? Or when you ran your finger along the edge of an envelope?
Which injury caused you the longest-lasting sting?
Why do paper cuts not bleed but hurt more than knife cuts?
A recent study published in the journal Physical Review E in August provided some answers. Researchers conducted a series of experiments to identify which types of paper are most likely to slice into our skin, causing the most painful and longest-healing wounds.
So, what types of paper are they?
The research was conducted by engineers from the Technical University of Denmark. They utilized finger models made from a special type of gelatin that simulates human skin tissue.
This material is commonly used in weapon studies, particularly to test the damage of projectiles. However, in this study, the Danish scientists wanted to pit it against an even older weapon: the edge of paper.
Various types of paper, including napkin paper, newspaper, printing paper, book paper, cardboard, and photo paper, were tested. The scientists cut them into “blades” similar to utility knives, then sliced through the gelatin fingers at different angles.
The results showed that paper with a thickness of 65 micrometers and an angle close to 20 degrees is the most likely to cause cuts. The closer to this “sweet cutting point”, the higher the risk of cutting.
The sweet cutting point of paper.
Compared to these results, napkin paper (typically under 50 micrometers thick) is too thin to be sharp enough to cut. On the other hand, cardboard and photo paper (usually over 200 micrometers thick) are too thick to create a sharp edge.
The types of paper that can most easily cut human skin range from 100 micrometers down to 65 micrometers, including: book paper, A4 printing paper, newspaper, and particularly, a type of paper close to the “sweet point” is perforated fax paper.
However, the researchers noted that this fax paper belongs to an older generation of machines and is rarely used anymore.
Nevertheless, there is a thin item similar to fax paper that is still widely used today: envelopes. Envelopes made from paper with an average weight of 60 gsm (grams/m2) typically have a thickness ranging from 80 to 75 micrometers, thinner than regular A4 paper and close to the “sweet cutting point.”
Be careful when licking or running your finger along the edge of envelopes to seal them.
This explains why accidents involving envelopes are so common, and we must be particularly cautious when licking or running our fingers along the edges to seal them.
But here’s some good news: once the envelope is sealed, its outer thickness doubles, exceeding the sweet point.
However, scientists say this does not mean that the outer edge of the envelope or papers of similar thickness, such as sticky notes or cardboard, cannot cut you. It just means their risk is reduced.
Why do paper cuts hurt more than knife cuts?
To understand this, you need to zoom in on the edge of a piece of paper at least 100 times. At that magnification, you will see that the edge of a sheet of paper is not as smooth as you might think. It is a collection of thousands of sharp, jagged saw blades extending outward from the paper’s surface.
The cuts from these paper blades are very rough, not smooth like a knife, which is the first reason why they hurt more.
The lower the quality of the paper, such as that used for envelopes, the worse it is processed, leaving behind more jagged edges that cause more pain. This type of paper also tends to have chemical residues left over from processing. These chemicals can “rub salt” into your wound, making it feel worse than a knife cut.
The edge of a sheet of paper under 100X magnification.
The second reason paper cuts hurt more than knife cuts is that paper often knows where to cut your skin. The tips of fingers, lips, tongue, and cheeks are the most common locations for paper cuts. These are all areas with a high concentration of sensory nerve endings.
The density of nerves in these spots is many times higher than in other areas like the arms, legs, or back. This is because these organs require the most tactile feedback.
A paper cut on your fingertip will cut through more nerves. These nerves send a very high-resolution pain signal to your brain. Naturally, your brain processes these signals more thoroughly. “High resolution” is indeed unfortunate in this case.
Also related to the location, fingertips are areas that are frequently in use. While you are working, the wound from the paper cut may shift, causing you to feel pain again.
But the most subtle aspect of a paper cut lies in its depth. A paper edge is sharp enough to cut through your skin but dull enough not to cause bleeding. This creates the perfect condition to expose the severed ends of your nerves to the air.
Since blood cannot flow to the cut, it cannot seal the wound and clot to protect it. The wound remains continuously open, irritating the nerve endings exposed to air or saliva, sending rapid pain signals to your brain and causing you to feel intense discomfort.
An edge of paper sharp enough to cut through your skin, but dull enough not to make you bleed.
In addition to the physical effects, paper cuts can feel worse due to psychological reactions. Most of the time, they happen by accident, causing you to feel frustrated and exclaim: “Why does this always happen to me?”
Being hard on yourself can also lead to anger: “Why do I keep hurting myself?” Or the anxiety of getting cut by paper again can make you uncomfortable. Think about how you would feel if you had to seal dozens of envelopes while just having cut your tongue.
What lessons can you draw from this?
In their research, the Danish scientists used their findings to create a cheap, disposable, and environmentally friendly knife. They employed a 3D model to create the handle, then attached strips of paper 65 micrometers thick to the blade.
As a result, a tool the research team called Papermachete was born. Testing this disposable knife, the scientists found it could cut through apples, bananas, cucumbers, bell peppers, spider plants, and even chicken.
A knife with a paper blade that can smoothly cut through chicken.
If you don’t have a strip of paper exactly 65 micrometers thick, you can also replace the blade of this knife with envelope paper, newspaper, or A4 paper. However, be cautious with these blades. Once again, while they can cut cucumbers, they can also slice into your skin.
Keep this experience to pass on to your children; they need to learn the lesson about the edges of paper. That paper is not as harmless as it seems at first glance. Every sheet of paper under a microscope is jagged like a saw. And some types of paper are more likely to cause cuts than others, particularly envelopes.
Finally, if you still get cut by paper, what advice can you follow? Having thoroughly analyzed the causes of the painful sensation from paper cuts mentioned above, we can outline some steps to deal with paper cuts.
- First and foremost, the advice is to wash the cut as soon as possible with soap and water. This will reduce the risk of infection and help the wound heal faster.
- Next, you need to prevent your nerve endings from being exposed to the air by applying a bit of ointment.
- Finally, cover the wound with a bandage to minimize movement at the injury site and keep the wound clean.
And that’s the entire science behind paper cuts.
