Books That Rot

In some ancient libraries, books can literally be attacked by microscopic fungi capable of digesting paper, glues, or the leather of bindings. These molds appear especially when humidity, heat, and poor ventilation combine for several years. Some leave spectacular stains, others slowly destroy entire texts with almost no visible traces at first.

Ancient books constitute environments particularly vulnerable to mold. Paper, leather bindings, animal glues, and certain pigments offer organic materials easily exploitable by several species of microscopic fungi.

When relative humidity durably exceeds certain thresholds, invisible spores present in the air begin to develop on the surfaces of works. Historic libraries poorly ventilated or subject to infiltrations then become very favorable environments.

Certain molds produce characteristic colored stains ranging from gray to black through greenish or orange hues. Others remain almost invisible while profoundly weakening paper fibers. The problem concerns not only the aesthetics of works. Fungi progressively degrade the very structure of materials. Pages become brittle, inks diffuse, and some bindings slowly disintegrate.

Conservators today use very strict protocols to control temperature and hygrometry in heritage reserves. Contaminated books are sometimes isolated to prevent spore propagation. Certain species also pose health risks for restorers working directly on collections. The paradox is that several ancient libraries possess precisely the cool, humid atmosphere historically ideal for parchment conservation, but much less adapted to modern paper or industrial materials introduced later in certain bindings.