Making paper from wood is a fascinating process that transforms trees into the familiar material we use every day. Essentially, wood is broken down into a pulp which is then processed and formed into sheets.
The Journey From Forest to Paper
The journey begins with pulpwood, which are trees specifically harvested for papermaking. This raw material undergoes several key stages to become the finished product.
Here are the primary steps involved in converting wood into paper, based on the process utilized in mills:
1. Raw Material Storage
The process starts at the pulpwood yard, where the harvested wood logs are stored. This serves as the initial holding area for the raw material before it enters the main processing stages.
2. Preparation: Debarking and Chipping
Next, the pulpwood is debarked, removing the outer layer of bark from the logs. After debarking, the wood is chipped into smaller, uniform pieces. This increases the surface area of the wood, making it easier to process in subsequent steps.
3. Pulping: Cooking the Chips
At the paper mill, these wood chips are cooked in a large vessel called a digester. This cooking process, often using chemicals, breaks down the lignin that binds the wood fibers together. The result is a thick slurry known as pulp.
4. Refining the Pulp
Once the wood has been reduced to pulp, it undergoes further treatment. The pulp is washed to remove residual chemicals and impurities. It is then typically bleached to achieve the desired brightness and color. Finally, the pulp is softened, making the fibers more pliable for papermaking.
5. Forming the Paper Sheet
The prepared pulp is mixed with a large amount of water. This dilute mixture is then pumped onto a moving screen within a paper machine. As the mixture moves along the screen, the water drains away, leaving the wood fibers behind to intertwine and form a thin mat.
6. Finishing: Pressing, Drying, and Smoothing
The mat of fibers, now a wet sheet, is then transported through a series of rollers and drying sections within the paper machine. The machines rapidly press, dry, and smooth the pulp. Pressing removes more water, and heating elements dry the sheet completely. Finally, calendering rollers smooth the surface, determining the paper's finish.
These steps transform rough wood fibers into a flat, smooth sheet of paper, ready for cutting and various uses.
