Photography is, in the grand scheme of history, a relatively new development. Yet even within a mere 150 years of existence, the form has changed drastically. Since its invention, photography has been through several different processes and chemicals and your collection could include rare prints from the 19th century, 35mm slides or an album of Polaroids.
This variety makes caring for photographic items complex and era-specific. If photography does not receive the appropriate care then it could be subject to fading, mould and other kinds of damage.
To combat 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 bring your galleries and stores as close to the ideal conditions as possible. This way, your precious collections can be preserved for future generations.
Creating a safe storage environment
Photographic items are most often kept in storage, where you can monitor and control the environment to protect your collections. If conditions in your store are poor, however, chemical processes of deterioration can slowly but 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. This happens through a loss of detail on photographs, middle tones and shadow areas, reducing the overall quality of the item.
Photographic chemicals react negatively to the changes in moisture and temperature. Gelatine emulsions can stick to other materials or grow mould in warm and damp conditions. Monitor the environment to ensure or adjust the correct conditions for the safe preservation of photographs.
Choose stores with naturally cool and dry environments. If necessary, introduce dehumidification equipment and limit the amount of staff working in the room.
Air can carry pollution in the form of gases and solid particles such as dust. Both of these 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 ensure minimum amount of dust in a store room. Sealed windows and doors help to reduce the dust in a store. Keep stored items in boxes or coverings to prevent the accumulation of dust.
Gaseous pollutants such as oxidant, sulphiding 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
When storing your photographic items, consider carefully how you will enclose them. Good storage enclosures, the materials that come into direct contact with photographic materials, will help to protect items from:
- Air-borne pollutants
- Rapid changes in environmental conditions
Most commonly, photographs are stored in folders, sleeves and boxes. Purchase enclosures from conservation suppliers to ensure that they are made from high-quality, non-polluting materials. These cost more, but contribute to preserving photographic items in the highest standard possible and protect them from damage.
Desirable qualities for storage enclosures
If storing photographic items in paper or card, acceptable materials include 'Silversafe' or ‘pHoton’ paper, unbuffered 'museum', or 'conservation' board or unbuffered acid-free tissue. Find 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 recommend for storing 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, as previously outlined, in the form of a sleeve, envelope or wrapper
- The second layer of 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 buffers them from adverse 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.
Suggestions for storage formats
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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 indelible 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 or piling up works. A ‘chinagraph’ pencil (available from art shops) also writes well on glossy surfaces.
When incorrectly handled, photographic items can become torn and dirty or suffer abrasion. Uncovered hands can also transfer skin oils onto photographic emulsions, irreparably damaging the work. When handling prints and negatives directly, wear clean cotton, latex or nitrile gloves.
Take particular care with negatives, as they do not have a margin around the emulsion.
Display photographic items with all of the same principles applied to storing them. Taking photographic collections out of storage, however, comes with the fresh challenge of lighting them.
All types of photographic materials are sensitive to light to some degree and exposure to light can cause fading, discolouration and degradation. For an in-depth look at lighting your collections, read our guide.
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 is 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 helps to preserve valuable photographic items and allows you to light displays brightly. Copies are also made for sale to the public. Process such copies normally.
If you are 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 being done very 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 is 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.
Museums Galleries Scotland have written a number of other advice guides on the storage, display and preservation of museum collections. Alternatively, contact us with any questions. For further reading, visit the Collections Trust.
- Care and Identification of 19th Century Photographic Prints (Reilly, J. Eastman Kodak Ltd,1986, ISBN 0879853654)
- The Care of Photographs (Remple, S. Lyons and Burford, 1987, ISBN 0941130487)
- The Permanence and Care of Color Photographs: traditional and digital color prints, color negatives, slides, and motion pictures (Wilhem H. Preservation Publishing Company, 1993, ISBN 0911515011 / 0911515003) Available online.
- The National Trust Manual of Housekeeping (Butterworth-Heinemann; The National Trust 2006 (Revised 2011) ISBN 978-1907892189)