yellowing newspapers

Newspapers use the cheapest paper and cheapest inks to keep the cost of publishing the news down. Newsprint falls into the category of "groundwood" paper with its primary components being cellulose and lignin. The cooking process removes lignin and it is the lignin content of groundwood that quickly yellows on exposure to light. The acidic lignin breaks down the molecular structure of cellulose, too, which weakens the paper.