If you suspect mould on books or documents, the priority is to avoid making it worse. Do not wipe, spray, seal or handle affected items without specialist guidance. Keep people away from affected material, avoid disturbing the growth, and contact a conservator promptly. The storage room itself may need a separate moisture assessment.
Distinguish a spot from active growth
An old discolouration, a faded stain and actively growing mould require different responses. The Library of Congress describes active mould as fuzzy or slimy, while dormant mould is typically dry and powdery. However, appearance alone cannot reliably confirm whether growth is active. Do not rub, press or touch the surface to test it. A conservator assesses the state of the mould and determines what handling is appropriate.
Do not blow on, brush or shake suspected mould. Disturbing growth releases spores into the air and onto nearby items.
What to do first
- Note the condition without disturbing the material. Is it wet, damp or dry? Where is the growth, and how far has it spread? Record this for the conservator.
- Keep people away from affected items. Mould can affect those with allergies or respiratory conditions. Do not handle affected material without specialist guidance on containment and protective equipment.
- Do not seal damp or mouldy books in plastic at room temperature. The NEDCC (Northeast Document Conservation Center) cautions that sealing mouldy materials without freezing can accelerate growth in trapped moisture.
- Do not spray, bleach, microwave or oven-dry books. These methods damage paper, bindings and inks.
- Contact a conservator promptly. For wet, valuable, archival or official records, a paper or book conservator advises on material-specific handling, containment and drying. A conservator may use freezing for wet or actively mouldy materials as a stabilisation step, but it is not a cleaning method and spores can remain viable afterwards. Follow their instructions rather than general online advice.
Irreplaceable items versus everyday books
| Type of item | Practical approach |
|---|---|
| Irreplaceable documents, photographs or rare books | Contact a paper conservator before attempting any cleaning. Handle as little as possible. Keep isolated in a dry, ventilated space. |
| Everyday paperbacks and replaceable books | If heavily affected and the cost of conservation exceeds replacement, discarding may be the practical choice. Still fix the room problem first. |
| Files, folders and office paper | Do not handle legal, archival or official originals without conservator guidance. For standard replaceable prints, the decision depends on the extent of contamination and whether the room moisture source has been addressed. |
Is it mould or booklice?
Small, moving insects on books are not mould. Booklice (psocids) are tiny, pale creatures that feed on microscopic mould and starchy surfaces. They thrive in the same humid conditions. If you see movement, it is an insect question, not a mould-cleaning question. Four Solutions' booklice assessment covers identification and treatment. Do not diagnose booklice from a photograph alone.
Check the storage area
Mouldy books usually point to a storage problem: a damp room, poor ventilation, a leaking pipe or wall seepage. If the room's moisture problem remains unresolved, surviving or replacement books may develop mould again.
The US EPA stresses fixing water problems and drying all items. The condensation-or-leak guide helps identify whether the dampness comes from condensation, a water leak, or both.
Who handles what
For the books and documents themselves, a paper or book conservator is the right specialist, especially for irreplaceable items. For mould on the walls or ceiling of the storage room, or for a persistent humidity problem, Four Solutions can assess the moisture source and treat the affected surfaces.
The wardrobe mould guide covers a similar split for belongings stored in wardrobes and cupboards.
Frequently asked questions
Can I wipe mould off a book with a damp cloth?
Do not wipe or rub suspected mould. Disturbing growth can spread spores to nearby items. A conservator can assess the state of the mould and recommend appropriate methods.
Should I freeze all my mouldy books?
Freezing is a stabilisation step a conservator may use for wet or actively mouldy materials. It is not a cleaning method and spores can remain viable afterwards. Do not freeze books as a routine step without conservator advice.
Is the musty smell dangerous?
Mould can affect people with allergies or respiratory conditions. Ventilate the area and avoid prolonged exposure. Consult a health professional if you have concerns before handling affected items.
Can Four Solutions treat the books?
Four Solutions assesses and treats mould on walls, ceilings and room surfaces. For the books and paper themselves, a paper or book conservator is the appropriate specialist.