Caring for photographic collections
Photography has evolved significantly since its invention in the 1800s. Photographers have experimented with different techniques and chemicals to capture, develop, and print their work. As a result, museum collections can include everything from early glass plates to albums of Polaroids.
This variety makes caring for photographic items complex and era-specific. If photography doesn’t receive the appropriate care, it can become subject to fading, mould, and other kinds of damage.
To prevent this, museums need to:
- Provide the correct environmental conditions
- Ensure that storage materials are stable
- Train staff in safe handling and display
Take the correct precautions and make practical adjustments to provide the most ideal conditions possible in order to protect your collections.
Creating a safe storage environment
When photographic items not on display or actively being engaged, they should be kept in storage, where you can monitor and control the environment to protect your collections. However, if conditions in your store are poor chemical processes of deterioration can slowly and irreversibly damage your items. Photos can become faded, discoloured, mouldy, brittle, or take on a layer of silver mirroring.
- Relative humidity should be stable between 30 and 40%
- Temperature should be stable below 16ºC
- No light except for access
- Air quality should have reduced particular and gaseous pollutants
- Materials should be museum-appropriate and chemically inert
- Accessible and organised storage
Relative humidity and temperature
Photographs fade at a much faster rate when the relative humidity rises. Fading causes a loss of detail in photographs, middle tones, and shadow areas, reducing the overall quality of the item.
Photographic chemicals react negatively to changes in moisture and temperature. Gelatine emulsions can stick to other materials or grow mould in warm and damp conditions. Monitor the environment and adjust accordingly to ensure the correct conditions for preserving photographs.
Choose stores with naturally cool and dry environments. If necessary, introduce dehumidification equipment and limit the number of staff working in the room.
Air can carry pollution in the form of gases and solid particles such as dust. Both can adversely affect the chemicals in photographic items, resulting in fading, embrittlement, discolouration and the weakening of binding layers.
Develop a comprehensive cleaning rota to prevent a build up of dust within the store room. Make sure windows and doors are sealed and keep stored items in boxes or coverings to prevent the accumulation of dust.
Gaseous pollutants such as oxidant, sulfiding, 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
- Photocopy machines
Identify the source of pollution then isolate or remove it from the collection. Molecular sieves in paper and card products, made by companies such as MicroChamber®, can trap airborne pollutants. Use molecular sieve products for sleeves, folders and boxes when storing photographic items.
Safe materials for enclosure
Carefully consider how you’ll enclose photographic items when storing them as photographic materials will come into direct contact with their storage enclosures. Good storage enclosures will help to protect items from:
- Air-borne pollutants
- Rapid changes in environmental conditions
Photographs are most commonly stored in folders, sleeves, and boxes. Purchase enclosures from conservation suppliers to ensure they’re made from high-quality, non-polluting materials. These cost more but contribute to preserving photographic items at the highest standard possible and protect them from damage.
Desirable qualities for storage enclosures
Recommended materials for storing photographs in paper or card include ‘Silversafe’ or ‘pHoton’ paper, unbuffered ‘museum’, or ‘conservation’ board or unbuffered acid-free tissue. Use MicroChamber® paper products to include pollutant-trapping molecular sieves in your enclosures.
Look for these qualities in paper and card enclosures:
- Free from wood pulp fibres, acids, and lignin
- Made from 100% cotton fibres or have a high percentage of alpha cellulose fibre content
- Neutral pH levels between 6.5-7.5
- Free from sulphur, peroxides, metal particles, and harmful sizing agents
Paper and card are recommended for the storage of photographic items. However, plastic is an acceptable alternative if the relative humidity of storage conditions is kept low.
Plastic enclosures should be:
- Free from plasticisers and coatings
Acceptable plastics include polyester film (Melinex 515 by ICI or Mylar D by Dupont), cellulose triacetate and polypropylene. Check suppliers’ catalogues for in-depth information on storage materials.
Storage formats and handling
Photographic items are normally stored within 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
Choosing the correct format depends on the size and shape of the object, as well as the limitations of your museum’s store. Having three layers around photographic items protects them from fluctuations in the environment and protects them from harmful conditions.
Shelving and cabinets in the storeroom should ideally be made of steel with a baked enamel finish. Wood, and especially composite boards, can give off high levels of gaseous pollution that could damage the collection.
Stores should be designed with safe and easy access in mind.
See our guidance on Creating and Improving Stores for tips on how to improve museum storage.
Every layer of packaging, from shelf numbers to individual sleeves, needs to be clearly labelled in a museum store.
Use appropriate labelling equipment, such as an HB or 2B graphite pencil, for marking accession numbers on the back of photographic prints. For permanent markings or to write on smooth surfaces without leaving a mark, use waterproof drawing ink with a very fine nib. Leave waterproof ink for a long time to dry before touching it. A ‘chinagraph’ pencil (available from art shops) also writes well on glossy surfaces.
Photographic items can become torn and dirty or suffer abrasions when incorrectly handled. Uncovered hands can also transfer skin oils onto photographic emulsions, irreparably damaging the work. Wear clean cotton, latex, or nitrile gloves when handling prints and negatives directly.
Take particular care with negatives, as they don’t have a margin around the emulsion.
Display photographic items with all the same principles which are applied to their storage. Taking photographic collections out of storage comes with the additional challenge of exposure to light.
All types of photographic materials are sensitive to light to some degree and exposure to light can cause fading, discolouration, and degradation. Read our guide on lighting your collections.
Follow these basic guidelines to minimise damage when lighting photographic items:
- Maintain a light intensity of 50 lux for all photographic material except modern black and white photos. Reduce the display time if it’s impossible to keep light levels this low.
- Eliminate ultraviolet radiation or keep it below 10 microwatts per lumen.
- Limit display time for photographic items – we recommend six months every four to five years.
- Keep collections in the dark outside of visitor hours.
Displaying copies instead of originals will help to preserve valuable photographic items and allow you to light displays brightly. Copies can also be made for sale to the public.
If you’re making a copy of a loaned item, the copy will become a unique record within the collection and should be treated with archival standards. This creates a stable artefact and reduces the degradation of the items. Archival processing involves changing chemicals before they become exhausted and washing out residual chemicals thoroughly.
Detailed instructions on how to carry out archival processing are available from literature on photography, good photographers, and photographic suppliers. The archivally processed material should be cared for in the same way as the rest of the photographic collection to prevent it from becoming damaged.
Dealing with cellulose nitrate
Cellulose nitrate is a chemical compound commonly used as the base material for films and negatives between 1889 and 1939. It’s also an incredibly unstable material and is entirely unsafe for display and storage.
Cellulose nitrate comes with two major problems. Firstly, it gives off harmful gases as it degrades. Secondly, the decaying process makes it increasingly flammable, catching fire at temperatures as low as 48ºC. It burns rapidly and gives off toxic and combustible nitrogen oxide and carbon monoxide.
Cellulose nitrate can be identified by its date, by degradation characteristics, and by a spot test. If you identify some in your collection, remove it from the museum and destroy it under the consultation of fire safety officers. If you wish to copy the material, contact a qualified expert.
See this page on Hazards In Collections which gives further information on identifying Cellulose Nitrate.