Paper is an important necessity in our lives to carry out our everyday work. We use paper for multiple reasons like writing, communicating, recording data, connecting, and entertaining each other; the uses are endless. But have you ever thought, how is this paper made and why are some paper different in texture or color?
Let’s dig into the papermaking process, which actually starts from wood. How can wood be turned into sheets of paper? The process of papermaking will tell each process involved in converting wood into paper. Most modern papermaking industry now uses old paper, waste wood fiber from sawmills, cloth made from plant material, vegetable matter, and recycled fabric to produce recycled paper. This recycled paper is excellent in quality and safe for the environment as it does not involve cutting down trees.
How paper is made step by step?
Whether you produce from wood or recycled products, there are three main steps involved in paper making process:
- Pulping
- Papermaking
- Finishing
Each of these main steps can be further divided into several processes before getting the paper product. Let’s look into each step in detail:
Step 1: Pulping:
Pulping is the process of making pulp which can be considered the first by-product produced to make paper. The pulping process can be a bit different for wood and recycled products as raw materials.
In the case of using wood as the raw material, the following will be the pulping process:
1. Debarking and chipping:
The chopped-down wood received at the paper mill is first thrown in a tumbler where they are debarked. For each plant or tree chopped down, the paper industry owner must plant new trees to have less effect on the environment. Chopping down trees can severely impact the environment, which must be thought about before chopping down the trees.
Coming back to debarking process, the barks must be removed as they cannot be used in the papermaking process. Water used in this process is filtered on the spot and is reused for other logs as well to reduce water wastage. The debarked logs are then chipped into small pieces by a grinder for further use.
2. Chemical and Mechanical Pulping:
The wood chips now move onto the next step, where they are cooked in a chemical solution. The process takes place in a huge vat known as digesters. In the digester, the wood chips are boiled in a sodium sulfide and sodium hydroxide solution at high pressure to break down the chemical known as lignin. As a result, the pulp is produced. Pulp is like a thick slurry and can be said as the initial raw form of paper.
3. Cleaning:
The pulp is then filtered to remove any impurity and unwanted particles. At this stage, any additional chemicals like bleach or color can also be added. After cleaning and screening, this pulp is then dried to be used for the production of bulk printing products. The pulp needs to go under several more processes to be converted into paper.
If the raw material being used to prepare pulp are recycled products, then the following will be the pulping process:
1. Producing pulp:
All the recycled products used for producing paper are mixed into processed water in a giant vat known as a pulper. The water and recycled papers and products are stirred to make a fiber suspension. All unnecessary particles and impurities are removed so that only fine-quality paper can be produced. Any additional chemical that needs to be added to the pulp can also be added at this stage.
2. Diluting the fiber solution:
After producing the pulp, the next step is to dilute the fiber suspension. This is done to produce thin and uniform paper, which are the qualities of a high-grade paper. In the initial stage of the papermaking process, the fiber solution is made very dilute; it comprises 99% water while only 1% is fiber.
Step 2: Papermaking:
After the production of clean and screened pulp, the process of papermaking can start. The machine generally used in the paper industry is the Fourdrinier machine; this machine was invented in England and was an advanced form of the paper machine first developed in France. This machine is now used in most paper industries for the mass production of paper. The machine is very large and can be as huge as four times the length of an Olympic pool. The height of the machine is as tall as a three-story building. The machine has several sections which cater to a different process of converting pulp into paper. Let’s have a look at the sections of the machine:
1. Head box:
Water from the diluted solution needs to be removed now, and the fiber in it needs to take a proper knitted shape to become paper. A horizontal slit squirts this liquid uniformly onto a moving wire mesh or forming fabric.
2. Wire section:
The thin fiber solution has now taken the form of a thin sheet over the revolving wore mesh. This step is also known as sheet formation. There are hydrofoils present beneath the wire mesh that helps to get rid of the excess water and enhance the uniformity of the fiber. This step also ensures that the threads are weaved tighter, strongly, and tightly so that the result is a strong paper.
This wire mesh also moves over suction boxes that help to remove further water from the pulp. After travelling 30-40 meters on the wire mesh, the water in the pulp drops to 75-80%; as a result, the pulp takes the form of a soft mat and no longer has the wet sheen to it. This soft mat is also referred to as paper web.
3. Press section:
Water in the web still needs to be removed; for this reason, the soft mat is passed onto a series of nip rollers and compressors that squeeze the excess water out of the mat. After all the squeezing, the water content reduces to 45-55%. The pressure exerted on the soft mat also enables the fiber to intertwine more strongly to form a uniform, smooth and dense sheet. The water removed from the soft mat is then recycled to reduce water wastage.
4. Drying:
The web still has not taken the form of paper, and water needs to be dried out. For this, the paper web is heated in enclosed chambers that have drying cylinders. They heat up to 130ºC with steam heat and dry out the excess water from the web. At this stage, only 15-20% of water is left on the web, and the web has come closer to being called paper.
At this point, different sizing solutions can be added to alter the opacity and finish of the paper. Different sizing solutions include starch, gums, and rosins, which can be added depending on the requirement. After the sizing, the sheet is further heated over another drying cylinder, and after travelling about 400 meters, only 5-7% of the water is left at the drying end.
Step 3: Finishing:
The dried paper still has to go through finishing touches to be used for different purposes. Here are some steps involved in this process:
1. Paper finishing:
The dried paper is then passed onto soft or hard rollers depending on the type of paper required. Films of different chemicals can also be applied to get the kind of paper desired.
2. Quality control:
To make the process more efficient, an automated measuring device is used to check the quality of the paper. The entire sheet of paper is monitored very finely to avoid any imperfections. Real-time monitoring over the different variables in the entire process is also being done to ensure that the end product is of the highest quality.
3. Paper winding:
The final tested paper is then rolled into giant paper rolls that can be more than seven meters long and can weigh around sixty tons before leaving the paper machine. These rolls are then passed onto a winder, where they are unwound and cut into desired sizes.
Conclusion:
The entire papermaking process is an interesting and complex process that converts wood or recycled products into high-quality, usable paper. The papermaking process involves many steps, and the chemicals involved in the process can be altered according to the type of paper required.
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