Best Practices for Cleaning and Removing Stains from Library Collections

Every library collection collects more than just knowledge over time. It also collects dust, grime, fungal growth, and stains that slowly eat away at paper, leather, and cloth. Cleaning these materials is not the same as cleaning your home. A wrong move with water, an aggressive brush, or the wrong chemical can cause permanent damage to a book that has survived for decades. This post walks through the safe, tested methods conservators use to remove dirt and stains, the products that work under controlled conditions, and the point at which a damaged item should leave your hands and go to a professional.

Why cleaning needs a careful, measured approach 🔗

Dust is not harmless. It is a mix of organic and inorganic particles, including skin cells, fibres, pollen, and soil, that settle on surfaces and attract moisture. When dust sits on paper, it holds humidity against the material and creates the exact damp conditions that mould and fungi need to grow. Dust also contains abrasive grit that scratches surfaces during careless handling. Research on university libraries has repeatedly found that dust and particulate matter are among the greatest causes of deterioration in collections.

The guiding principle in all conservation cleaning is minimal intervention. You remove only what is harmful, you use the gentlest method that works, and you always test on a small, hidden area first. Many cleaning processes, especially stain removal, are irreversible. Once paper fibres are weakened or a stain bleeds outward, there is no undo button.

Dry cleaning techniques for dust and surface dirt 🔗

Dry cleaning is the first and safest step. Because no moisture is introduced, the risk of activating mould or warping paper stays low. This is where most routine library cleaning should begin.

Vacuum cleaning for dust removal 🔗

A vacuum cleaner is the workhorse of dust removal, but not the household kind. Conservators recommend a vacuum with a low suction setting, a soft-bristled brush attachment, and a HEPA filter that traps fine particles instead of throwing them back into the air. Specialised book-cleaning systems connect to HEPA vacuums that can filter dust particles down to 0.3 microns, which protects both the material and the person doing the work.

The method matters. Hold the book firmly shut so dust does not fall between the pages. Brush gently from the spine outward. A useful safeguard is to place a piece of cheesecloth or fine screening over the nozzle so that any loose fragments, such as flaking leather or paper, are not sucked away. A face mask is essential, since you will be disturbing dust and possibly mould spores.

Brushes, cloths, and conservation erasers 🔗

For surfaces that a vacuum cannot fully clean, soft brushes and lint-free cloths take over. Static or microfibre cloths lift dust without leaving residue. One firm rule is to avoid chemically treated dusting cloths, because they leave an oily film on paper and binding that attracts more dirt over time. Stubborn surface grime on sturdy paper can be reduced with specialised conservation erasers, such as vinyl or kneaded erasers, used lightly so the paper fibres are not abraded.

Removing fungus with cotton swabs 🔗

Fungus and mould need targeted, careful handling. First, the item should be dried and the mould rendered inactive before any removal, because disturbing active mould spreads spores. After vacuuming away the loose, dormant growth through a screen, the mechanical method uses soft brushes, cotton swabs, and small tools to lift residue from delicate areas. Cotton swabs are ideal for tight spots like the joints of a binding, where mould often hides at the head and tail of the spine.

When the paper and media can tolerate it, a swab lightly dampened with a solution of ethanol with about 20 to 25 percent water added can inactivate spores. The water makes spores more vulnerable to the fungicidal effect of the alcohol. Always test first. Alcohol can dissolve certain inks and damage coated or glossy papers, so an inconspicuous corner is your testing ground every single time.

Dealing with crusts and hardened deposits 🔗

Sometimes dirt, old adhesive, or fungal matter dries into a hard crust on a surface. Scraping a dry crust risks tearing the paper underneath. Controlled humidity helps here. Carefully introducing a small amount of moisture or steam can soften a hardened deposit enough to lift it gently, without soaking the material. This is delicate work. Too much moisture reactivates mould and weakens fibres, so it is done in tiny, controlled amounts and followed immediately by thorough drying. For anything beyond a minor deposit, this crosses into treatment that belongs in trained hands.

Stain removal under controlled conditions 🔗

Stain removal is the riskiest part of cleaning, and it should only be attempted on stable materials after dry methods have been exhausted. Different stains demand different responses, and there is no universal solvent.

Fungus stains and localised bleaching 🔗

Even after mould is killed and removed, it often leaves behind dark yellow, brown, or purple stains caused by its metabolic waste. These are stubborn. Many conservators find that the only way to reduce them is through careful, localised bleaching. The conservator may apply a dilute bleaching agent, such as a measured mix of water with hydrogen peroxide or a weak bleach solution, using a cotton swab and test-dabbing in a safe area first.

The dangers are real. Bleaching can bleed the stain into surrounding paper or over-oxidise and embrittle the sheet. After bleaching, the area must be rinsed with repeated dabs of clean water so no oxidiser is left behind, then blotted as dry as possible. Many institutions caution against chemical bleach altogether, because bleach can cause paper to deteriorate rapidly in humid conditions and the stains often return. This is precisely why bleaching is a last resort, not a first response.

Ink, water, and other stains 🔗

Ink stains vary by type. Ballpoint ink may respond to ethanol or acetone applied on a swab, though complete removal is rarely possible. Iron gall ink, common in historical documents, is a different problem entirely. It corrodes paper from within and usually needs stabilising treatment rather than removal. Water stains, which appear as yellowish-brown rings where dissolved dirt collected at the edge of a dried wet area, can sometimes be reduced through controlled washing with distilled water, but this is an immersion process best left to specialists.

The non-negotiable rules of any treatment 🔗

A few rules apply to every stain you touch. Test on a hidden area first. Use the mildest solution that could work. Apply chemicals sparingly, because over-saturation weakens paper and can promote further mould growth. Disinfectants like 70 percent isopropyl alcohol or thymol carry their own risks to inks and paper and require knowledge to use safely. And never spray or saturate a book directly with bleach or solvent.

When to call a professional conservation laboratory 🔗

The most important conservation skill is knowing your limits. Some items and some damage simply should not be handled by library staff. Rare, valuable, or fragile materials warrant professional treatment from the outset. Extensive staining, severe pest infestation, large-scale mould outbreaks, and anything involving immersion washing belong in a laboratory. Immersion and chemical bleaching carry significant risks of irreversible loss, and the value of a damaged but intact item almost always outweighs the gamble of a botched home repair.

For institutions, there is an established national resource. The National Research Laboratory for Conservation of Cultural Property (NRLC) in Lucknow, established in 1976 under the Ministry of Culture, specialises in conservation science and provides research, technical assistance, and training to museums and cultural institutions. The NRLC is the premier body for the conservation of museum, library, and archive collections, and it has standardised methods for treating many types of material. The National Mission for Manuscripts also supports the conservation of written heritage and connects holders of valuable documents with trained conservators.

Before sending anything out, do not pull badly damaged material from the shelves and pile it up. Instead, record the call numbers and a note on the problem, isolate affected items so mould does not spread, and contact a conservator for guidance on transport and handling.

Prevention reduces the need for cleaning 🔗

Every cleaning treatment carries some risk, so the smartest strategy is to need less of it. Maintaining stable temperature and humidity, filtering air, washing hands and using gloves when appropriate, storing fragile items in acid-free boxes, and running scheduled inspections all reduce how often interventive cleaning is required. Fragile or brittle books that cannot survive routine handling are best protected inside a custom enclosure rather than cleaned repeatedly. A collection that is well housed and regularly checked stays healthier and demands far fewer of the risky treatments described above.

What do you think? If you found a valuable old book in your college library with visible mould stains, where would you draw the line between cleaning it yourself and sending it to a conservation laboratory? And how much should a library invest in prevention versus treatment when budgets are limited?

References

1. https://www.conservation-wiki.com/wiki/BPG_Mold
2. https://digitalcommons.unl.edu/libphilprac/6511
3. https://search.library.wisc.edu/digital/A27AR3PDDBFNCP9B/text/AY5K2TGDLGOWE39B
4. https://www.alphatch.com/portable-library-book-cleaning-machine/
5. https://www.reganagency.com/important-cleaning-procedures-for-libraries/
6. https://www.nature.com/articles/s40494-023-01083-3
7. https://inspectapedia.com/mold/Moldy_Book_Cleaning.php
8. https://chinapreservationtutorial.library.cornell.edu/content/mold/
9. https://boneybooks.com/how-to-get-mold-off-books
10. https://culture.gov.in/our-organisations/national-research-laboratory-conservation-cultural-property-lucknow
11. https://indianculture.gov.in/MoCorganization/national-research-laboratory-conservation-cultural
12. https://www.namami.gov.in/