How to Care for and Preserve Rare Books: The Complete Guide
The physical preservation of a rare book collection is a form of investment protection. A book that deteriorates from fine to very good condition loses 40–60% of its value. A book that develops mold, insect damage, or severe foxing can become essentially worthless as a collectible. Yet the basic principles of book care are simple, inexpensive, and effective — they require attention and consistency rather than specialized equipment or expertise.
Environmental Control
Temperature
The ideal temperature range for book storage is 65–72°F (18–22°C). Higher temperatures accelerate chemical degradation of paper and binding materials. Lower temperatures are acceptable but can cause problems when books are moved to warmer environments (condensation forms on cold surfaces, creating moisture damage).
The critical rule: Avoid temperature extremes and rapid fluctuations. A steady 75°F is better for books than a room that cycles between 60°F and 85°F.
Humidity
The ideal relative humidity (RH) range is 30–50%.
Too dry (below 30% RH): Paper becomes brittle, leather bindings crack, and adhesives dry out and fail. This is a common problem in centrally heated homes during winter.
Too humid (above 60% RH): Mold growth, foxing (brown spots on paper caused by fungal activity and/or iron compounds reacting with moisture), and insect infestation are all promoted by high humidity.
Monitoring: A digital hygrometer (available for $10–$30) provides real-time humidity readings. Place one in the room where your books are stored and check it periodically.
Mitigation: A dehumidifier (in humid climates) or a humidifier (in dry climates) can maintain the appropriate range. Air conditioning provides both temperature and humidity control.
Light
Light is the enemy of books — particularly ultraviolet (UV) light, which causes fading, yellowing, and chemical degradation of paper and ink.
Direct sunlight: The most damaging light source. Never store books where sunlight reaches them directly. Even indirect sunlight near windows causes cumulative damage.
Fluorescent lighting: Fluorescent bulbs emit significant UV radiation. If your book storage uses fluorescent fixtures, consider replacing them with LED bulbs (which emit negligible UV) or adding UV-filtering sleeves to the tubes.
Display lighting: If you display books, use low-wattage LED lighting positioned away from the books. Limit display time — rotate displayed books periodically rather than leaving the same books on permanent display.
Air Quality
Airborne pollutants — dust, tobacco smoke, cooking fumes, industrial emissions — deposit on paper and accelerate degradation. Store books in a clean environment with good air circulation. Do not store books in kitchens, garages, or rooms where smoking occurs.
Handling
Clean Hands
Handle rare books with clean, dry hands. Oils and moisture from skin transfer to paper and binding materials, causing staining over time. Some conservators recommend cotton gloves for handling very valuable items, though others prefer clean bare hands (gloves reduce tactile sensitivity, increasing the risk of accidental damage).
Opening
Open books gently. Do not force a book to lie flat — this cracks the spine and damages the binding. For books that resist opening, support the front and back boards with your hands and open only as far as the binding allows naturally.
Page Turning
Turn pages from the top corner, not the bottom. Do not lick your finger to turn pages (moisture and acids from saliva damage paper). Do not use paper clips, Post-it notes, or rubber bands as bookmarks — all leave residue or cause indentation.
Moving Books
When moving a book from a shelf, grasp it by the middle of the spine (supporting the entire book) rather than pulling it by the headcap (the top of the spine), which tears the spine cloth.
Dust Jacket Protection
Every dust-jacketed book should be fitted with an archival Mylar (polyester) jacket protector. Mylar is chemically inert, transparent, and provides a physical barrier between the jacket and the environment.
Sources: Brodart, Gaylord, and other archival supply companies sell pre-cut Mylar jacket protectors in standard sizes. Custom sizes can be cut from rolls.
Application: Wrap the Mylar around the jacket and fold the excess around the inside of the boards. The protector should fit snugly but not tightly — too tight causes the jacket to buckle.
Cost: Approximately $1–$3 per cover. A trivial investment that provides significant protection.
Common Threats
Foxing
Foxing — the brown or reddish-brown spots that appear on paper — is caused by a combination of fungal activity and chemical reactions involving iron compounds in the paper. It thrives in humid environments and on papers manufactured with certain chemical processes (particularly papers from the mid-nineteenth to mid-twentieth century).
Prevention: Maintain humidity below 50% RH. Treatment: Professional conservators can reduce foxing through chemical treatment (bleaching), but the process is expensive and may alter the paper’s character. For most collectible books, foxing is accepted as a condition flaw rather than treated.
Sunning
Sunning — the fading of cloth bindings, dust jacket colors, and spine lettering caused by light exposure — is the most common condition problem for twentieth-century first editions.
Prevention: Store books away from direct and indirect sunlight. Use UV-filtering glass or acrylic in bookcases with glass doors. Treatment: Sunning cannot be reversed. Prevention is the only option.
Mold
Mold grows on books stored in humid (above 60% RH), warm, poorly ventilated environments. Mold appears as fuzzy or powdery growth on paper, cloth, or leather — typically white, gray, green, or black.
Prevention: Maintain humidity below 50% RH and ensure good air circulation. Treatment: If mold appears, isolate the affected books immediately (to prevent spread). Air-dry the books in a well-ventilated space. Brush off dried mold spores with a soft brush outdoors. For severe infestations, consult a professional conservator.
Insect Damage
Bookworms (actually the larvae of several beetle species), silverfish, cockroaches, and termites all feed on paper, binding materials, and adhesives.
Prevention: Keep storage areas clean and dry. Inspect books periodically for signs of insect activity (small holes in paper, fine powdery residue, live insects). Store books in sealed bookcases if insect activity is a concern. Treatment: Isolate affected books. Freeze treatment (placing the book in a sealed bag and freezing for 72 hours) kills most book-eating insects. For severe infestations, consult a pest-control professional who specializes in cultural property.
When to Seek Professional Help
Professional book conservators can repair damaged bindings, stabilize deteriorating paper, clean soiled pages, and restore damaged dust jackets. Conservation treatment is appropriate for valuable books with specific problems — but it should be performed only by trained professionals.
Finding a conservator: The American Institute for Conservation (AIC) maintains a directory of member conservators. Look for conservators who specialize in book and paper conservation.
Cost: Conservation treatment typically costs $100–$500+ per book, depending on the complexity of the treatment. The cost is justified when the treatment preserves or restores significant value.
Disclosure: Any conservation treatment performed on a book should be disclosed when the book is sold. Undisclosed restoration is a form of misrepresentation.