Can the page yellowing on books spread to other books?

Question:I was cleaning off my bookshelf the other day, when I noticed that a fairly new book (I might have bought it a few months ago, I haven't read it yet) had a lot of page yellowing. It was next to an older book, which has dark yellow pages. Did the page yellowing spread from the old book to the new book? What caused it? Should I separate my old and new books from now on?

Answers:
Yellowing pages are caused by the acid level of the paper. The higher the acidity, the faster the pages will yellow and become brittle. Generally speaking, paperbacks and lower quality hardbacks will use more acidic paper than higher-quality hardbacks.

Acidity cannot be transferred from one book to the next. However, if you put a piece of acid-free paper in close, prolonged contact with an acidic piece, that can cause the acid-free sheet to yellow from the contact with the acid in the acidic one.