Books, documents, maps, prints and postcards are likely to suffer damage if they are placed on display, whether as part of an organised exhibition, or in domestic circumstances. Various measures can be taken to help prevent this.
Display increases the risk of vandalism. Showcases need to be of substantial construction and should be fitted with strengthened glazing set in rebates which face inwards. Suitable floor and wall fixings should be provided, and security locks fitted where appropriate. Supervise access to the display area and, unless night security is very good, remove items over night to a secure area. Ground floor windows and doors are obvious weak points. The local Crime Prevention Officer will be able to give advice on this and other security measures.
In general a constant temperature within the range 13°C to 20°C and a constant relative humidity within the range 35% to 60% is required. This should be frequently monitored. A simple thermometer can be used for measuring temperature, and relative humidity, which is the measurement of moisture in the air, can be checked using a hygrometer. In hot dry conditions bindings and documents will become brittle and inflexible, and at the other extreme, excessive moisture will promote mould growth. Avoid displaying items near obvious sources of heat such as hot water pipes, direct sunlight and above fireplaces and radiators, and encourage good ventilation to help eliminate stagnant air pockets.
Exposure to both natural and artificial light will cause serious harm to books and documents. Not only will inks and colours fade but paper and binding materials will also deteriorate. The amounts of both visible light and of ultra violet emissions from the sun and fluorescent lighting will need to be controlled to a reduce this damage. This is best accomplished by displaying items in a windowless room, reducing the overall amount of artificial light to the barest minimum and incorporating UV absorbing filters into the display glazing. Alternatively fit UV absorbing films to windows and fluorescent lighting. Curtains and blinds can be used over the windows to control light or to cover the display when not being viewed. If illumination is necessary then lighting must be carefully chosen, and sited outside of the display unit so as not to cause a heat gain inside. It should be remembered though that all light falling on an object for any length of time will cause damage.
Showcases and picture frames will provide physical protection for the items to be displayed. The use of wood and board in their construction will minimise climatic fluctuations inside the display. A small amount of air must be allowed to enter the showcase and frame to regulate relative humidity, but atmospheric pollution must be excluded. A seal should therefore be made between the glazing and rebate, and around back panels, using a suitable porous material such as gummed paper. Where necessary provide showcases with a few small ventilation holes and fit them with cotton wool or fibreglass filters to exclude dust and dirt. Glass, polymethyl methacrylate (Perspex) or polycarbonate (Marlon) can be used for display glazing. Their various qualities should be carefully considered before a choice is made. Although glass is relatively cheap and does not easily scratch, it can break and cause damage; it provides little protection against UV light, is heavier than the plastic alternatives and moisture can condensate on it and encourage mould growth. Non-reflective glass is particularly susceptible to the later. Polymethyl methacrylate provides an excellent UV barrier, does not shatter and is light, but it scratches easily. Polycarbonate is similar. If glass is used for glazing, a sheet of Perspex, three millimetres or more in thickness, should be placed immediately behind it. This will form a UV barrier and provide physical protection to the item should the glass break. No glazing material, protective sheets or films should be placed directly in contact with the displayed items as this will lead to damage caused by abrasion, and pressure through people leaning on display. In picture framing, fillets of wood or card frames are placed around the item to prevent contact with the glazing.
It is absolutely essential that all materials and adhesives used in mounting the display are of conservation quality, free from acids, chemical impurities and harmful additives. Harmful products such as pressure sensitive tape and board containing mechanical wood pulp should not be used. The displayed items must be allowed to expand and contract freely. On no account therefore should adhesives, dry mounting film or drawing pins be used to fix items directly to the base. Books should preferably be displayed on books supports or cushions, with open pages retained by use of strips, cords and ribbons made of polyester, silk, linen or cotton. Documents, postcards and prints can be secured in place in a similar manner, or by the use of suitable photographic corners or paper hinges fixed to the reverse of the document with starch paste.
Documents bearing inks, colours and pigments that are in an unstable, flaky or powdery condition should be referred to a specialist for advice on their display.
Remember to seek specialist advice if there is any doubt about the suitability of a display area or the appropriate methods and materials to use. The professional services of qualified paper conservators and picture framers who are on the Conservation Register or members of the Fine Art Trade Guild are recommended. Both organisations have adopted guidelines and codes of practice for conservation framing which should be specified when you have any work undertaken.
A list of suppliers of materials and equipment is available.