Identifying Mold on Paper

Book with mildew damage.

No items with mold, mildew, or insect infestation will be accepted in MLAC.

As stated in the Packet for Depositing Libraries:

"All items must be free of loose dust and debris. No items with mold, mildew, or insect infestation will be accepted."

MLAC will also not accept items that have been treated for mold because of the potential that mold spores may still be present.

Definitions

Mold

Most of us associate mold with the furry stuff that grows on food left too long in the refrigerator. While it can appear on books like this, particularly after a major water leak or flooding, it also shows up in more subtle forms and in a variety of colors. Gray or black spots will often indicate mold, especially if coupled with a musty odor. However, mold can be any color depending on the material upon which is growing.

Book with mold damage.

Gray or black spots will often indicate mold, especially if coupled with a musty odor.

As defined by the Environmental Protection Agency, spores are "the means by which molds reproduce. Spores are microscopic. They vary in shape and range from 2 to 100 microns in size. Spores travel in several ways: passively moved by a breeze or water drop, mechanically disturbed (by a person or animal passing by), or actively discharged by the mold (usually under moist conditions or high humidity)."

Mold spores are present everywhere and only need suitable conditions to develop into mold.

Mold derives its food (and its color) from the substance on which it forms; for example, the materials of a book. During their growth they produce citric, gluconic, oxalic, or other organic acids that can damage paper, leather, cloth, etc. They also at times produce color bodies, leading to staining which is difficult to remove.

Mold and Mildew are the same thing. They are both a type of fungi. Though many of us use the terms interchangeably, mildew refers to a disease of plants. Different types include Downy Mildew (also called False Mildew) and Powdery Mildew.

What Causes Mold to Develop?

Book with mold damage.

High temperatures plus high humidity seem to be the biggest culprits in causing mold.

  • Water leaks or spills
  • High humidity
  • Warm temperatures
  • Stagnant air and dim light
  • Chemical composition of material
  • Any combination of these conditions

Barring a large leak or flooding, high temperatures plus high humidity seem to be the biggest culprits in causing mold.

General guidelines suggest keeping the temperature between 65°-75° Fahrenheit and relative humidity between 45%-65%. "However, some common molds can grow at temperatures as low as 50° Fahrenheit and in relative humidities as low as 45%." (Source)

For more detailed information on humidity, temperature and the additional factors that contribute to mold growth, continue reading Invasion of the Giant Mold Spore by Sandra Nyberg (Solinet Preservation Leaflets).

She covers these topics extensively as well as providing useful and in-depth information on prevention and suggestions for environmental modifications for your building or environment. As she states: "maintenance of proper environmental conditions will prevent mold growth." (Source)

Health Issues Related to Mold

Mold protection gear.

You should wear disposable rubber or plastic gloves, a lab coat and a respirator whenever handling moldy materials.

Some of the molds commonly found in library and archival collections can cause serious health problems including respiratory infections, headaches, nausea, and eye and skin irritation. People predisposed to upper respiratory problems such as allergies and asthma should not be exposed to areas affected with mold, even if they wear a respirator.

For health reasons, even a small mold outbreak should be taken seriously. You should wear disposable rubber or plastic gloves, a lab coat and a respirator whenever handling moldy materials. Ordinary dust masks are not sensitive enough to filter mold spores, use a respirator with a HEPA (high efficiency particulate arrestant) filter.

Be aware that respirators are ineffective if used improperly; for example, people with facial hair will not be protected because they can't get a tight fit. Training staff about proper fitting and use of respirators is essential. Wash protective clothing in hot water and bleach. (Source)

Several websites provide great information on a variety of topics related to the preservation of books and paper. CoOL: Conservation OnLine (a project of the Preservation Department of Stanford University Libraries) and the "Conservation Advice" section of the State Library of Victoria are especially helpful and user friendly.

CoOL provides an easy to use index and the State Library of Victoria has Information Guides on everything from packing and storing books to suppliers of conservation material and equipment.

Learn More

MLAC: A Virtual Tour

Bib the Book icon.

Take a slideshow tour of the Minnesota Library Access Center from the book's point of view, hosted by Bib the Book.