Old books often have a faded yellow/golden hue giving them a unique timeless aura. Ever wondered why their pages turn yellow?
Photo by Pixabay
The yellow tinge you find in old newspaper clippings, letters and book pages has a simple scientific explanation to it.
Paper is mostly made from wood and wood has a substance cellulose and Lignin in it. Cellulose is the substance plant cell walls are made of and is good at reflecting light while lignin gives the cell walls their rigidity and strength.
Why paper is white to start with?
Since cellulose reflects light, we see that as “white” color and it is the reason why paper usually comes in white color.
Why do white pages turn yellow?
Lignin’s molecular structure changes when exposed to light and surrounding air. Thus both lignin and in part cellulose, are vulnerable to oxidation by oxygen in the surrounding air. Oxidation breaks the bonds holding the subunits in the polymer chains of lignin creating molecular regions called chromophores.
Chromophores reflect certain wavelengths of light and each wavelength of light corresponds to a certain color. In case of lignin’s oxidation, the chromophores reflect the color yellow or a slight brownish color.
So there’s not much you can do to keep your favorite books from turning yellow other than keeping them in a vacuum!