Caring for photographic collections

Photography has evolved significantly since its invention in the 1800s. Photographers have used different techniques, materials, and chemicals to capture, develop, and print their work. As a result, photographic collections are wide-ranging and can include:

• Glass plates and lantern slides
• Daguerreotypes
• Negatives
• Prints on paper: calotype, salted paper, cyanotype, albumen, platinum, Woodburytype, gelatin, colour chromogenic
• Prints on glass: collodion, ambrotype
• Film
• Albums
• Associated equipment and cameras

This variety makes caring for photographic items complex and era-specific. These materials can form part of an archive or exist as individual collection pieces. Many museums are now digitising photographic collections to improve access while reducing handling of unstable originals.

For advice on caring for paper-based items, the MGS guide to caring for paper collections covers storage, handling, and environmental conditions in detail.

Photographs are extremely sensitive to their environment. Without appropriate care, photographic items deteriorate through chemical, biological, or physical damage, including:

• Physical damage from handling, poor storage, crushing, tearing, or abrasion to emulsion surfaces
• Environmental factors, including fluctuating relative humidity, temperature, light, and air pollution
• Pests and micro-organisms such as mould
• People, including biological deposits from handling, and loss from theft or fire
• Materials in direct contact with objects in storage or display
• The quality of the object itself, from its manufacture, past display, storage, or use

Photographs consist of many different layers, materials, and manufacturing processes. In unsuitable conditions they can become extremely unstable, with complex issues that differ for each item.

To prevent damage and slow deterioration, you need to:

• Provide the correct environmental conditions for storage and display
• Make sure storage materials are stable and chemically inert
• Train staff in safe handling and display

The sections below cover each of these areas in detail.

How to create a safe storage environment

Store photographic items out of the light when they are not on display or in active use. Use packaging to give them additional protection.

Monitor and control the environment in your store. Poor conditions speed up chemical deterioration and can slowly and irreversibly damage items. Photographs can fade, discolour, grow mould, become brittle, or develop silver mirroring.

Original boxes, albums, and sleeves may need different conditions from the photographic items themselves. Decide whether separating them would better preserve the material. Document everything before separating items to prevent dissociation.

Aim for:

• Stable relative humidity between 30-40%
• Stable temperature below 16°C
• No light except during access
• Reduced particulate and gaseous pollutants
• Museum-appropriate, chemically inert materials
• Accessible and well-organised storage

How does temperature and humidity damage photographs?

Photographs fade faster as relative humidity rises. Fading causes loss of detail, particularly in middle tones and shadow areas, reducing the overall quality of the item.

Photographic chemicals react badly to changes in moisture and temperature. Gelatin emulsions can stick to other materials or grow mould in warm, damp conditions. Our guide on monitoring your museum environment provides advice on how to adjust conditions accordingly.

Choose stores with naturally cool, dry, and dust-free environments. Introduce dehumidification equipment where needed and limit the number of staff working in the room.

How does air quality damage photographs?

Air carries pollution as gases and solid particles such as dust. Both damage the chemicals in photographic items, causing fading, embrittlement, discolouration, and weakening of binding layers.

Develop a housekeeping plan to prevent dust build-up in your store. Make sure windows and doors are sealed and keep items in enclosures, boxes, plan chests, or filing cabinets to prevent dust accumulation.

Gaseous pollutants such as oxidants, sulphide gases, or acidic gases can come from:

• Vehicle emissions
• Wood, wood products, and finishes
• Newly applied oil-based paints
• Poor-quality paper products
• Some plastics, especially cellulose nitrate
• Poor-quality foam
• Some textiles and rubber
• Poorly processed photographic materials
• Some cleaning materials
• Photocopiers

Identify the source of pollution and isolate or remove it from the collection. Molecular sieves in paper and card products, such as MicroChamber®, trap airborne pollutants. Use molecular sieve products for sleeves, folders, and boxes when storing photographic items. These also prevent images from sticking together if material becomes wet or degrades.

Our guide to identifying and reducing air pollution explains the different types of pollutant and how to control them.

How does light damage photographs?

All types of photographic materials are sensitive to light to some degree. Exposure causes fading, discolouration, and degradation. The MGS guide to conservation and lighting explains how to set appropriate light levels and reduce cumulative damage.

Follow these guidelines when displaying photographic items:

• Maintain a maximum of 50 lux for all photographic material except modern black and white photographs. Reduce display time if you cannot keep light levels this low.
• Eliminate ultraviolet radiation
• Limit display time — no more than six months every four to five years if kept in optimum conditions throughout
• Keep collections in the dark outside visitor hours

How to store photographic items

Store photographic items in three layers:

• The first layer of direct-contact materials: a sleeve, envelope, or wrapper
• The second layer: a box, folder, or drawer
• The third layer: on a shelf or in a cabinet

The right format depends on the size and shape of the object, its condition, and the limitations of your store. Three layers protect items from environmental fluctuations and harmful handling.

Make shelving and cabinets from steel with a baked enamel finish where possible. Wood and composite boards give off high levels of gaseous pollution that can damage collections. The MGS guide to creating and improving stores has practical advice on designing storage spaces for safe and easy access.

Displaying photographic collections

Apply the same principles to display as to storage. Taking photographic items out of storage introduces the additional challenge of light exposure, including task lighting. The light guidance above applies equally here.

Using copies

Displaying copies instead of originals preserves valuable items and allows you to use higher light levels. Copies also give the public access to images as a resource. Make copies as good quality as possible, as copying images repeatedly carries risks. Treat facsimiles and negatives with the same archival standards as the rest of your photographic collection.

Copies can also be made for sale to the public.

If you copy a loaned item, the copy becomes a unique record within the collection. Archival processing involves changing chemicals before they become exhausted and washing out residual chemicals thoroughly. Detailed instructions are available from photography literature, experienced photographers, and photographic suppliers. Care for archivally processed material in the same way as the rest of the collection.

How to handle photographic items safely

Photographic items tear, collect dirt, or suffer abrasions when handled incorrectly. Oils from uncovered hands transfer onto photographic emulsions and cause irreversible damage. Wear clean, close-fitting nitrile gloves when handling prints and negatives directly. Always handle items from the edges and never touch the image or emulsion side.

Take particular care with negatives, which have no margin around the emulsion.

Keep items in their sleeves, folders, or storage enclosures wherever possible to reduce risk. Always move the enclosure rather than pulling on the photograph itself to remove an image.

Cellulose nitrate is a chemical compound used as the base material for films and negatives between 1889 and 1939. It is highly unstable and entirely unsafe for display or storage.

Cellulose nitrate presents two major risks. It gives off harmful gases as it degrades. It also becomes increasingly flammable as it decays, catching fire at temperatures as low as 48°C. It burns rapidly and gives off toxic and combustible nitrogen oxide and carbon monoxide.

Identify cellulose nitrate by its date, degradation characteristics, and a spot test. If you find any in your collection, remove it from the museum and arrange destruction in consultation with fire safety officers. Contact a qualified expert if you need to copy the material first.

The Hazards in Collections website has further information on identifying cellulose nitrate.

Label every layer of packaging clearly, from shelf numbers to individual sleeves.

Use an HB or 2B graphite pencil to mark accession numbers on the back of photographic prints. For permanent markings or writing on smooth surfaces, use waterproof drawing ink with a very fine nib and allow it to dry completely before touching. A chinagraph pencil, available from art suppliers, also works well on glossy surfaces. The Collections Trust guidance on labelling and marking museum objects has further advice on safe marking methods.

Photographic materials are especially vulnerable in a fire or flood. A robust, active emergency plan that identifies hazards and sets out how to reduce or respond to them is essential.

The Scottish Council on Archives has produced emergency planning guidance for collections with practical advice on preparing for incidents.

Scotland has dedicated networks for specialist help during emergencies. Find contact details on the Scottish Council on Archives page listing emergency response networks across Scotland.

For more collections care guidance, read our other advice guides on collections.

The Collections Trust provides a wide range of guidance and advice on collections care, including their publication Standards in the museum care of photographic collections, which covers recommended conditions for storage and preservation.

The Institute of Conservation offers collections care advice for photographic materials.

The Library of Congress has produced a detailed guide to care, handling, and storage of photographs.