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.