It turns out that roll on the wall is less a household item and more a quiet agreement between chemistry, marketing, and our own weird psychology.  Paper starts out as mashed plant fibers—cellulose—from trees or recycled  paper. Mixed with water, it becomes a pale, gloopy slurry. But trees also contain lignin, the brown “glue” that holds them together. Leave the lignin in, and the paper turns beige, stiff, and yellows with time.