Most modern paper is made from trees, but that hasn't always been the case. In fact, paper can be made from any form of cellulose that can be broken down into fibers.
What Is Cellulose?
Because cellulose is what gives all plants their structure, most plants can be used to make paper.
Since the Chinese produced the first true paper around the year 100 A.D., people have made paper with rags, old fishing nets, grass, tree bark, and a variety of other plants.
Starting The Process...
To begin the process, the cellulose has to be boiled, beaten, or shredded into tiny fibers. The paper pulp, made up of those tiny fibers is then spread into sheets, pressed, and dried to make paper.
To make strong paper, you need long fibers which is why the pulp has to be beaten instead of chopped. Beating the cellulose separates the fibers from each other, while leaving individual fibers intact.
Sticking Together And Bonding
The reason cellulose molecules in paper stick together after they're wet is that they are made of long strings of glucose molecules one of the components of common table sugar.
When cellulose is beaten into a watery pulp, some of the glucose molecules dissolve in the water. Then, when the pulp is spread in a sheet to dry, the glucose re-bonds with the cellulose molecules to hold the paper together.
The strongest and most permanent paper would be made entirely from long fibers of pure cellulose.
But, because paper comes from a variety of natural materials that are made of much more than pure cellulose, other chemicals, mixed in with the cellulose weaken the paper and cause it to break down faster.