Book Collecting Guide

Identify, Prevent, and Remove Mold and Mildew from Books

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!

prevent and remove mildew


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!


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.

Archived comments

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  1. Franklin Mint Archives Antiquarian

    Amber, thank you for the wonderful and insightful article. All this time I thought it was an industry “secret”. I had been using my own remedies for various illnesses, some worked and some, not so well. I am a second generation collector, I got stuck with my Mothers ancient collection (which I came to LOVE), but I am also a fixer, so if there is a problem, I will find a way! You just made my life so much simplier, thank you! Sincerely, Xanthe V

  2. Alex Roy

    Thanks lots for Sharing Wonderful information for me and every one who are facing these types problems It is very useful for me because
    i am facing these problem please tell me which companies offering the service of mold removal in Winnipeg

  3. Mold removal in Markham

    It is a good article about mold.Thanks for sharing this.It is helpful for me as i have been searching the solution to get rid of molds for a long time.It will be very helpful for those who are facing this problem.I saw mold inspection on my favorite book and i am quite worry now a days.But reading your article now i have a great idea to get rid of mold.Thanks.

  4. Mold removal in Moncton

    I have already suffered from this mold. My plenty of books already spoiled by mold. Now i am taking extra care of my books. Main thing i keep on my mind is humidity. Humidity is one of the main reason of production of mold. Thanks for this information about identify,prevent and remove mold from books.

  5. Top Rated Dehumidifiers

    Wonderful article to kill molds and mildew! Well, I got a dehumidifier and I can say that it is really one of the best and most effective way to prevent and remove moisture in the air that produces the molds! And I recommend this as well to my friends.

  6. Kristi Knight

    I have yearbooks that were in a flood several years ago and ended up getting mold on them. How can I repair these or have them repaired? There are 3-4 books and many pages stuck together. Does your company do this or do you know of a company that does this?
    Thanks for your help!

  7. mold testing guy

    Once you have mold in your books, you should check other areas of your home. This is no joke. People get really sick from mold.

  8. Petar

    If your books ever get wet from a home flood be sure to put the book in the freezer until a professional can take care of it. IPADS don’t freeze at all! smile . . .

  9. MJ

    Dehumidifiers can help in reducing your mold and mildew. Great article very informative. Books are always the first thing to get moldy or newspapers. The moisture has certainly spread.

  10. Christine Robins

    Thanks for some excellent advice. I will try some of your tips.

    Two corrections:

    1. You write that molds and mildew live on “inorganic” material. You mean “organic”, i.e. things that were once alive, such as paper or leather.

    2. The possessive form of “it” (meaning “belonging to it”) is neither “its’” nor “it’s”, but “its”.

  11. Miles

    very useful post and it is very important to know about mildew and mold and even difference between them.

  12. Elsa M. Lopez

    Do you recomment products such as lysol for cleaning books. Besides lysol, what other products may be used?

  13. Dana A. Lewis

    Great article. Also good to remember that school textbooks almost always have this mold. I’m severely allergic to it and it ruined my 12 yrs of public school. So if you have a student who’s showing symptoms (running nose, post nasal drip, itchy throat, or the feeling of ants crawling all over, get them some help.

  14. Clarissa Andrews

    This was very informative. I appreciate you finding the time and energy to put this information together.

  15. Martha Dawson

    How does black mold affect the value of an otherwise collectable book? Is it best to try to remove the mold? In my case, the mold is very slight, hardly visible to the eye, but there’s a slight musty odor.

  16. Cheryl

    Silica gel is an important way to reduce moisture and smells. I isolate the book in a plastic box. Silica gel sprinkled on the backs of book shelves or in boxes is also a way to prevent silver fish.

  17. Rob

    Was really delighted to receive info on how to detect and tackle ‘bookworm mold’, etc. But, what about ‘foxing’ — What is it and how can that be treated? Many thanks!

  18. Marc de Piolenc

    I had to learn much of this the hard way when my mother’s basement, holding nearly all my books, was flooded many years ago. I would have given much back then to have the Internet, and your resource on the Net, to steer me to the right solutions. One question: is there a method, usable by an individual, for activating powdered charcoal? Where I live now there is excellent quality coconut charcoal available, but it is not activated and the activated product has to be imported.

  19. Keith Harris

    Have any of the reader ever tried putting a book in a very quick visit to a microwave oven? One should experiment with a spoiled or cheap book first. I did it fews times but only for a few seconds. It appeared to work but I have never compared notes to see if it was a permanent fix. Any comments?

  20. Patsy Davis

    Thank you for this useful information. I have a very smell book bought recently so I will try the bicarbonate of soda before giving up.

  21. Sam

    Nice post.. But the the most important thing in mold cleaning is that you should eliminate the source of moisture that has allowed moisture to creep into your house. Molds can create breathing problems for you and your family members, serious mold infection can lead to bronchitis and asthma

  22. Kathie

    I was told that water damage that is now bone dry on a few pages of a book will cause the book to mildew when it is put in storage. Is this possible?

  23. jackson

    hey, what if the damp book was left to dry by itself and shows yellow stain on it? any ways to remove it? Thanks..