Conservation materials commonly used in AH&P
Since their invention in 1839, photographs have become such a common feature of most people’s lives that it is easy to forget how vulnerable they are. When considering how to handle, care for, store, and display your photographs it may be helpful to bear in mind that a photographic image is the result of a chemical reaction which occurs when light-sensitized material is exposed to light. Most importantly, this chemical reaction does not stop once the image has been captured, it is merely temporarily interrupted. So from that point onwards the length of a print’s life depends, amongst other things, on being able to prevent this chemical reaction from continuing until the image is lost. This is done primarily through limiting exposure to heat and light. Despite a photograph’s seemingly robust appearance, it is probably the least durable and most easily damaged of all image types.
Of course, a photograph can be created by one of many processes, and images have been made on a variety of materials ranging from glass and paper to metal or plastics. While each photographic process is unique, and photographs can vary dramatically in appearance and format, there are things which can be done to help preserve them for as long as possible.
Some of the following have already been mentioned in the previous blog post, they are included again here for completeness sake.
- Ensure hands and working surfaces are clean, dust-free and dry and only hold photographs, slides, and negatives at the very edges. Finger prints cannot be removed and attract dirt so, ideally, white cotton, vinyl or nitrile powder free disposable gloves should be worn.
- Try to keep items on a flat surface for support and, when carrying items from place to place, use a box lid or tray – particularly if you are working on large photographs, glass negatives or lantern slides. If you have a large collection of photographs and again particularly if you are working with glass negatives, it may be worth covering a stiff piece of card with several layers of white tissue and using it as a work surface. You can tear off a layer of tissue as it becomes dirty and the pad you have made will act as a cushion should you accidentally lose your grip on the glass.
- Do not force curled/folded items open as this will cause damage. If your photographs are loose and beginning to curl, store them face down to stop this from getting worse until you can put them into sleeves or mount them.
- Cased photographs such as daguerreotypes should not be dismantled even if only to change a damaged cover glass. The image on the support surface is not ‘fixed’ and the slightest disturbance will cause irretrievable loss. It is advisable to seek the advice of a Conservation professional regarding care and storage of these items.
- Do not leave your photographs out in the light unnecessarily. Cover prints you are not working on or looking at – or turn them face down. Even short bursts of exposure to light will contribute to a photograph fading and colour photographs are especially vulnerable.
- Avoid marking photographs with ink (which fades, can bleed if damp, or mark neighbouring images). If necessary use a 2B pencil to lightly write on the reverse of the image. It is better to label along an edge, so that any accidental marks made by pressing too hard will not appear through on the actual image. If you find that a soft pencil does not work well or smudges – as the backs of modern photographs are coated with slippery resin – you might consider putting your photograph into a polyester sleeve and slipping a labelled piece of acid-free paper in at the back.
- Do not use sticky labels, even on the backs of photographs – the adhesive in these can cause damage, can be difficult to remove, and, if the photographs are stored in batches, can adhere to other prints.
- The surface of a photograph can be dusted lightly with a very soft brush made from natural hair. Dirty or dusty mount boards can be cleaned using a soft eraser, using small circular motions, but this should not be used on the actual photograph. Be sure to remove all eraser ‘droppings’ with a soft brush.
- Take care not to touch the emulsion side of negatives. They are easily marked and scratched and even a soft brush can cause damage. Lantern slides, however, have a cover glass to protect the emulsion side so these can be gently cleaned with a soft brush before packing into acid-free** paper enclosures such as the ones pictured above.
Some storage guidelines
- As when storing any documents you wish to keep safely, avoid using elastic bands. They may perish or stick to items causing staining and scratching as well as damaging the edges of prints.
- Avoid the use of metal pins and paperclips as they can rust and tear items.
- Never use adhesive tapes for repairs as they can dry out and peel, cause staining, and adhere to other things.
- Avoid storing photographs in plastic ‘magnetic’ albums with adhesive surfaces, as these do not allow items to ‘breathe’ and trap any chemicals released during the degradation process to create a ‘pressure cooker’ effect, ultimately accelerating decay. Photo corners or ‘pocket’ albums are preferred. Also avoid contact between facing images. To provide protection for your photographs, album pages can be interleaved with acid-free paper** to prevent abrasion. Take care, however, not to overfill the album with the additional paper as this may cause the spine to crack and break the binding.
- If possible avoid dismantling albums unless the photographs are deteriorating badly. You risk causing more damage in doing so. If you do decide to dismantle an album for whatever reason, remember to record any inscriptions and note the original order that the prints appeared in the album.
- Store different types of materials (photographs, negatives, paper documents, objects, textiles etc) separately, keeping a note of items which belong together.
- Do not use plastic and PVC wallets, plastic/bin bags or cling film for storage as these yellow and become sticky with age, and can cause photographic items to ‘sweat’. Also avoid wooden storage boxes and drawers as they can contain chemicals which can transfer or react with photographic materials.
- Lantern slides and glass plate negatives should ideally be stored upright in boxes, with acid-free** card dividers in between every fifth plate. If they are stored flat in batches, stack a maximum of 10 small or 5 large items, as the weight of the ones on top may damage or crack the ones underneath. Large photographs on the other hand are better stored flat to prevent them from sagging. They can be interleaved with acid-free or silversafe paper to protect them from rubbing. Boxes should be well fitting, to prevent too much movement, but sufficient space should be left to avoid damaging items when removing or replacing them.
• If you have photographs in frames, check that the surface of the photograph is not touching the glass as it may become stuck to it in time. A mount will help to prevent this.
- Place your framed photographs where they will not be exposed to direct sunlight. Be aware that, unfortunately, all photographs out on display will fade over time, and colour photographs will fade much more quickly than black and white prints. You may consider making copies of certain images to have out on show and then the originals can be kept safely in storage.
- Photographs should be stored in cool, dark and dry conditions with stable humidity and temperature. A cupboard at the centre of a house and away from fireplaces, radiators and exterior walls, will provide the most stable environment. Areas such as sheds, garages, attics and basements are prone to sudden changes of temperature and may be damp or contain pests, so should not be used for storing photographic items.
These guidelines are by no means comprehensive and there is more detailed advice about caring for photographic collections available online. The National Archives website has a section devoted to the preservation of photographs and includes information about packaging as well as listing suppliers of conservation grade materials, and although the Preservation Advisory Centre closed at the end of March, their resources and publications are being transferred to the British Library Collections Care webpages. Icon (The Institute of Conservation) includes a Conservation Register of qualified conservators in the UK and Ireland.
• All materials must pass the PAT silver tarnish test (i.e. the Photographic Activity Test).
• Photos should be stored in non-buffered paper enclosures and boxes with a pH of 6 (neutral). 100% cotton fibre is recommended.
• Polyester (polyethylene-terephthalate) is recommended for sleeves, as it is glass clear, chemically inert, and does not contain ‘plasticizers’ or yellow with age.
• Mount boards should be 100% cotton fibre and all papers should be made of new ‘rag’ (cotton or linen) pulp, or fully bleached chemical wood pulp with a high alpha cellulose content (above 87%) and pH of 6-9.