Old letters, certificates, diaries and photographs are the heart of family history. They carry the handwriting, ink and stories of those who came before us. But paper is fragile, and heat, light, damp and clumsy handling can destroy these treasures far sooner than you might think. With a few simple habits, you can keep your family's documents safe for generations.

Why old paper decays – and what threatens it

Most paper made after the mid-nineteenth century contains acids from wood pulp. Over time, these acids break down the cellulose fibres, turning paper yellow, brittle and crumbly. Light, especially ultraviolet (UV) from sunlight, accelerates decay and fades ink. Damp encourages mould and foxing – those brown spots – while dry heat makes paper brittle. Pests such as silverfish and booklice feast on paper and glue. Oils, salts and dirt from our hands can permanently stain and weaken paper. Even a well-meaning repair with adhesive tape can cause more harm than good.

Handle fragile documents with care

Before you touch any old letter or document, wash your hands thoroughly with soap and water, then dry them well. Clean, dry hands are better than cotton gloves for paper because gloves reduce your sense of touch and can catch on brittle edges. Avoid hand cream, lotions and perfume, which can transfer to paper. Work on a clean, dry surface away from food and drink.

• Support the document with a rigid board or acid-free card. Never pick up a fragile page by one corner; slide both hands underneath.
• Do not fold, crease or bend stiff paper. If already folded, leave it and store flat if possible.
• Use a pencil – never a pen – for notes near a document, and write on a separate sheet.
• Keep food, drink and pets away from your workspace. A single spill can ruin a collection.

Store items in acid-free folders and boxes

The materials you store your documents in matter as much as the environment. Ordinary cardboard boxes, manila envelopes and plastic sleeves contain acids and lignin that will damage paper over time. Instead, look for acid-free, lignin-free archival folders and boxes. For most paper documents, choose buffered folders with a pH of around 8 to 9 – the alkaline buffer neutralises acids for decades. For photographs, blueprints and wool or silk items, use unbuffered folders (pH neutral) instead.

Store documents flat in folders, or upright in archival boxes if they are strong enough. Do not overfill boxes; documents should be snug but not tightly packed. For very fragile items, place them in polyester sleeves made from polyethylene terephthalate (PET). Avoid PVC (polyvinyl chloride) sleeves, which give off harmful gases. Never use adhesive tape, rubber bands, paper clips, pins or staples – they rust, stain and tear.

Create a stable, dark and dry environment

Where you keep your documents is critical. Lofts, cellars, garages and sheds are the worst places: they suffer extremes of temperature, damp and pests. Instead, store your collection in a living space with a stable temperature of around 16–20°C and relative humidity between 45% and 55%. A spare bedroom, a cupboard in a hallway or a dedicated archive room works well. Avoid direct sunlight and strong artificial light; UV rays fade ink and weaken paper. Keep documents away from radiators, fires, kitchens and bathrooms, where heat and steam can cause chaos.

If you live in a damp area, consider using a dehumidifier or silica gel packets (rechargeable ones) in storage boxes, but monitor humidity with a simple hygrometer. Mould can bloom above 65% relative humidity; below 30% paper becomes brittle. Good air circulation helps prevent mould, so don't seal boxes airtight unless you know the contents are perfectly dry.

Avoid tapes, lamination and DIY repairs

It is tempting to reach for sticky tape when a letter tears. Please don't. Adhesive tape – including so-called 'invisible' tape – yellows, becomes sticky, stains paper and causes surrounding fibres to tear as it ages. It also releases acids that burn the paper. Lamination may look protective, but it is irreversible and destructive: the heat and plastic encapsulate the document, and removal by a conservator is expensive and risky.

Similarly, avoid gluing, ironing, bleaching or using sticky tape. Never use rubber bands – they perish and fuse to paper. If a document is torn or brittle, place it in a polyester sleeve to prevent further damage and keep it flat. For serious repairs, consult a professional paper conservator. They can mend tears with wheat starch paste and Japanese tissue, which are reversible and safe.

Digitise for access, then store the originals safely

Digitisation is a wonderful way to share your family history without handling fragile originals. Use a flatbed scanner or a camera on a copy stand with soft, diffuse lighting. Scan at 600 dpi for documents and 1200 dpi for small details, and save as TIFF for master copies. Always handle the original carefully during scanning, supporting it on a board. Once digitised, store the files in at least two places – an external hard drive and a cloud service – and label them clearly with names, dates and places.

But remember: digital copies are not a substitute for preserving the originals. Keep the originals in their acid-free folders, in a cool, dark, dry place. Check them once a year for signs of mould, pests or damage. With a little care, your letters and documents will survive to tell their stories for many generations.