Imagine: You just came across a wonderful book in your favorite used book or thrift store, and it seems to be everything that you were looking for to add to your shelf. It is nearly perfect, except for the pervasive, dank smell that comes along with it.
Unfortunately, that smell can be an indication of improper storage in a cold, damp basement or uninsulated attic, leaving it open to the growth of mold and mildew. These fungi are the most common culprits of the familiar “old book smell,” but that odor is the least of the detrimental effects possible.
Mold and mildew live off of organic material (leather, wood, paper, cloth) and over time their presence can weaken the structure of the book, stain the cover and pages, and prompt negative effects in your health, especially for folks with allergies or asthma.
It is important to identify the active growth of mold and mildew and remove it before it spreads through your entire library!
Identification
Mold: Mold is a type of fungus that can and will grow on anything, as long as it can find a food source and the appropriate humidity for its development. It can develop in patches of threads, thick spider-webs or fuzzy spots, and it appears most often on natural, porous surfaces such as cotton, linen, silk, wool, leather, and paper. It reproduces by sending out clouds of spores, hence it's ability to “leap” from book to book.
You probably have mold growth on your book if you observe any of the following problems:
- the presence of fuzzy growth, in just about any color you can imagine
- stringy, white filaments stretching across porous surfaces
- evidence of past water damage
- strange spots or stains
Mildew: Mold is often accompanied by mildew. While they share some similarities, they are not the same kind of fungus. However, any moldy or otherwise soiled surface can provide a nutritive source for mildew, and beyond that it requires the prime temperature and humidity level to make it appear and spread like wildfire.
You probably have mildew growth on your book if you observe any of the following problems:
- “Old book smell” - that ubiquitous scent is often caused by mildew, even after it is removed
- a thin haze, a patch of spots, or a powdery flaking layer, normally white, black, or grey on the surface of the book or paper
If you identify mold or mildew on any of your books, magazines, or paper ephemera, remove them from your collection immediately!
Prevention
Humidity is the number one condition for the growth of mold and mildew. It is the moisture in still, quiet air that allows mold spores to grow and spread. Think of dank basements, musty attics, or clothes left in the washer too long – these are prime mildew-growing habitats.
- Keep your books on a shelf that gets a decent air flow, not in a closet, basement, or against an outside wall of the house.
- Maintain good air circulation by using fans. If possible, use an air conditioner during the hot summer months and a heater during the cold winter to maintain a temperature around 70 degrees Fahrenheit (21 degrees Celsius).
- A dehumidifier should help to keep the humidity under 60 percent, but only when necessary. Books that are too dry can be damaged and crack.
- While houseplants are a lovely addition to a room, your library might be better off without them; or at least keep them away from the bookshelves.
- Dust the tops of your books regularly, as a clean surface is less attractive to spores.
- Some book collectors swear by the light use of lavender essential oil directly on the bookshelf as it is an anti-fungal, but this will scent the books and may cause discoloration.
- It is also suggested to keep a small, electric light burning in your bookcase, but this can also cause discoloration to your books over time.
Care and Removal
Whether you are a casual bibliophile or a serious collector, your books likely mean a lot to you. If you do not feel confident handling your prized books in the following methods, please find a local conservator who can professionally clean your collection, or rebind them if all else fails.
Remember, mold and mildew can be harmful to you as well as to your treasured library! Please exercise caution, and wear a mask over your nose and mouth to reduce the impact on your health.
Removing Mold and Mildew growth from the Outside of a Dry Book:
- If you can perceive growth on your book's cover, you may use a fine brush or very soft cloth to gently brush away the mildew. Alternatively, a HEPA filter vacuum hose attachment with a thin cloth or dryer sheet over the nozzle can be an effective resource to remove mold growth from the book cover.
- For a paperback book you can use a soft cloth lightly dampened with denatured alcohol to kill the mildew. Use light, gentle strokes as not to damage the paper/glossy cover, and make sure that you dab away the excess liquid and dry the book thoroughly but gently.
- For a cloth, leather, or other hardback types of binding, you can spot-clean with denatured alcohol, but make sure to test an out-of-the-way corner to check for color change or deterioration.
Removing Mold and Mildew growth from the Pages of a Dry Book:
- Slide a sheet of waxed paper underneath the moldy page to protect the page behind it. As in the step above, use a soft brush to carefully remove any obvious mold or mildew. Dampen a soft cloth with hydrogen peroxide or denatured alcohol and carefully treat
Removing Mold and Mildew growth from a Wet Book:
- Do not attempt to brush or wipe mold off of your damp books, as it will likely smear and stain the surface, as well as grinding it further into your book. You MUST dry your book and then treat the mold problem afterwards.
If you are not able to work on drying and cleaning a damp book immediately, place it in a plastic zip-top bag and pop it in the freezer. Let it thaw once you are ready to try the following methods of drying your book:
- Place absorbent sheets (paper towels, rags, etc) between each page of the book and wrap the book in a towel. Set a heavy weight on top to squeeze out the moisture. You will need to replace the absorbent materials frequently. Repeat until the book is damp, not sopping.
- Air circulation is very helpful in drying your book. You can use fans or hair dryers to speed the drying process, but air directed at the books for an extended amount of time can cause warping of the cover, boards, and pages.
- If your weather is cooperative, place the books into the sunlight, as exposure to the sun’s UV rays can help to kill mold spores. Remember; however, that light can cause damage and bleaching, so bring in your books after an hour in the sun.
- You can dry a damp book completely by sprinkling cornstarch between the pages and letting it sit in a plastic bag or box for a couple of hours. The cornstarch will absorb the excess moisture. When you remove the book, use a soft brush to clean up the cornstarch and repeat as needed.
Musty odor still lingers after mold and mildew removal:
- If your book is mold and mildew free but still has a smell to it, you can sprinkle baking soda in a sealed container or bag and place the book inside for a couple of hours. The baking soda is quite effective at absorbing the scent. Activated charcoal can be substituted in this step. Again, repeat as necessary.
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