Open an old book and take a breath.

That warm, sweet, slightly dusty smell seems almost impossible to describe.

But it has a chemical explanation.

In Why Old Books Smell Sweet, we explore the surprising chemistry behind the scent of aging paper, ink, glue, and leather.

Paper is largely made from plant fibers containing cellulose. As books age, the materials inside them slowly break down through chemical reactions.

This process can release tiny airborne molecules known as volatile organic compounds, or VOCs.

Some of these compounds have sweet, vanilla-like, woody, or almond-like aromas.

One important example is vanillin, a compound also associated with the familiar smell of vanilla.

As certain components of paper and other book materials degrade, van ...