Cellulose is a polysaccharide that is produced by plants. It is incorporated into plant cell walls, giving the cell structure stability; it has some unique and useful properties for humans. It is durable and resists decomposition, making many plants, such as trees, ideal building material. Cellulose fibers cling to each other when soaked in water and continue to cling together in a mesh when dried. This characteristic of cellulose is what makes paper possible.
To make paper, the fibers are turned into a pulp and cleaned. The pulp can be formed mechanically or chemically. When formed mechanically, the pulp is pounded to break down the cellulose fibers. When formed chemically, chemicals are used to break down the fibers and remove a chemical called lignin. Lignin causes paper to yellow over time, and removing it results in a more stable paper that does not yellow. However, the mechanical method has a higher pulp yield. Some fibers contain very little lignin, notably cotton, which makes a very high-quality paper. After the fibers have been adequately broken down, they are added to water, roughly nine parts water to one part pulp. Other chemicals, such as pH buffers or bleach, are added to create different types of papers for different purposes.
Once prepared, the pulp is poured over a moving wire mesh. This removes water and causes the pulp to form a thin web of fibers. A special type of felt is pressed against paper web. The paper adheres to the felt and is lifted off of the wire mesh. A second sheet of felt goes over the paper, and the stack is pressed in rollers. Handmade papers, which do not use heavy machinery, often use a mold to create the paper. This involves dipping a wire mesh screen on a frame into a vat of pulp, shaking to remove any excess and smoothing the fiber web and then waiting for the paper to set up enough to be removed from the frame and placed onto felt.
Most commercial papers are dried by pressing the water out of paper using felt designed for paper. Papers are also heated in dryers that can reach 200 degrees Fahrenheit. Handmade papers are typically hung on poles or ropes to dry, or are dried flat. Drying in this manner can take several days or even weeks, depending upon the paper and conditions. After it has dried, paper can be cut into sheets, textured, marked or sized.