1. Why Torn Paper Has Fuzzy Edges
Try tearing a piece of paper gently. If you look carefully at the torn edge, you will see tiny, fuzzy fibers. This raises a curious question: what connects these fibers to each other within the paper? [1]
Many people assume that a glue-like substance is painted onto the fibers to hold them together. However, no glue is added to hold the fibers together. [1]
If there is no glue, how do the fibers stick together so firmly? To understand this, we must first look at what paper is made from. [1]
2. How Wood Is Turned Into Paper Fibers
Most paper today is made from wood chips, which are small pieces of crushed wood. These chips are cooked in a large vessel with chemicals like sodium hydroxide at 150 to 160 degrees Celsius (about 302 to 320 degrees Fahrenheit) for about 5 hours. [2]
During this cooking process, a substance called lignin, which originally held the wood fibers together, dissolves away. What remains is a mass of fibers, mostly cellulose, known as pulp. This process is called cooking or pulping. [2]
These separated fibers are the starting material for modern paper. [2]
3. The Force That Bonds Paper Fibers Together
To make paper, the pulp is mixed with a large amount of water and poured onto a wire mesh. The water falls through the mesh, leaving only the fibers behind to form a thin sheet. [3]
This sheet is then pressed to squeeze out more water and passed through hot rollers to dry it completely. [3]
As the water leaves the sheet, the fibers come close together. On the surface of cellulose fibers, there are many parts that attract water, called OH groups. When the paper dries, these OH groups on neighboring fibers pull directly toward each other and stick. [1]
This attraction is called a hydrogen bond. This is the answer to the mystery from the first section: paper is held together primarily by hydrogen bonds, not glue. [1]
Because of this, when paper gets wet, water enters the spaces between the cellulose fibers. The fibers swell up, and the hydrogen bonds that held them together loosen. This is why wet paper tears easily. [1]
SAFETY NOTE: Water passes through the mesh, leaving fibers as a thin sheet. [3]
4. How Paper Is Treated to Stop Ink from Spreading
Paper fibers have a natural tendency to attract water. If you drop ink on paper that has not been treated, the ink spreads through the gaps between the fibers, causing a blur. [4]
To prevent this, chemicals called sizing agents are used. These agents adjust how much water the paper absorbs and how fast it spreads. [4]
There are two main types of sizing agents. One type, called internal sizing, is mixed directly into the pulp to stop water from soaking into the inside of the paper. The other type, called surface sizing, is applied to the surface to increase surface strength and stop ink from blurring. [4]
Notebooks and drawing paper resist blurring because of these sizing agents. [4]
5. Why Japanese Washi Paper Lasts So Long
Japan has a traditional type of paper called washi. The plants used to make washi, such as kozo, mitsumata, and gampi, have fibers that are longer than the fibers in wood pulp. [5]
The fibers of kozo, for example, are about 3 times longer than wood pulp fibers, though the exact number changes depending on the material and measurement conditions. [5]
Longer fibers tangle together more easily, creating more points of connection. This makes the paper strong even when it is thin. The strength of paper depends not only on fiber length but also on the properties of the raw materials and the method of making it. [5]
Because of these qualities, some washi papers have survived for more than 1,000 years. In contrast, the lifespan of Western paper is said to be only a few hundred years. [5]
6. The History of Paper and How It Is Recycled
Paper was born in China more than 2,000 years ago. Around 105 AD, a government official named Cai Lun improved the process to create practical paper using hemp rags and tree bark. This paper was made using the same principle of fibers sticking together. [6]
The technology for making paper spread to the Islamic world after the Battle of Talas in 751. It is said that prisoners captured in this battle included people who knew how to make paper. From there, the technology slowly spread to Europe, reaching Spain by the 12th century. [7]
Today, used paper in Japan is collected and recycled into new paper. However, every time paper is recycled, the fibers become shorter. As fibers shorten, there are fewer places for them to tangle, and the paper loses strength. [8]
Paper fibers cannot be recycled infinitely. Depending on the type of paper and how it is processed, the approximate limit for reuse is about 5 times. [8]
Paper, born more than 2,000 years ago, still relies on this mechanism of fiber bonding in every sheet today. [8]
7. Try It Yourself: Paper Experiments at Home
If you want to investigate further, you can try these experiments at home with adult supervision.
Take some old paper and tear it gently. Use a magnifying glass to observe the cut edge. Look at the fuzzy fibers and compare the length and thickness of fibers in different types of paper.
Compare how easily dry paper tears versus paper that is slightly wet. You can feel how the hydrogen bonds loosen when the paper is wet.
Drop one drop of water on old copy paper, newspaper, or flyers. Compare how the water spreads or blurs differently on each type. [4]
SAFETY NOTE: Place a towel on the desk to prevent water spills. Do not tear books or notes you still need; use only unwanted paper. When tearing paper, keep the paper away from your face and handle it gently and handle the edges gently to avoid cuts. [1]