Photographs

Displaying photographs

Photographs on display can be affected by adverse conditions, just as they are when they are in storage. During display, however, there are added factors which can contribute to the deterioration of collections. These differences will be discussed in the following sections which deal with:

• how light affects photographs;

• the ideal conditions for displaying photographs;

• lighting hints;

• mounting and framing photographs;

• some easy do-it-yourself methods for displaying photographs; and

• the best materials to use for displaying photographs.

How does light affect photographs?

Light is essential in a display environment. But light, especially when it is accompanied by UV radiation, can cause extreme and irreversible damage to many types of photographs. Many components of photographs are adversely affected by light and UV radiation.

Paper can become brittle and yellow, especially if it contains lignin.

Proteins, such as albumen and gelatine emulsions are affected: albumen yellows and gelatine breaks down.

The dyes used in colour photographs fade when exposed to light. Dyes used for tinting many 19th century photographic prints fade very quickly because early synthetic dyes had very poor light-fastness.

Pink dye can still be seen at the lower edge of the image. The dye has faded in all other areas of the photograph. Photograph courtesy of Artlab Australia, reproduced with permission of Mortlock Library, State Library of South Australia

Faded photograph. Light can have an adverse effect on photographs, contributing to fading and yellowing. Photograph courtesy of Fred Francisco

Damaged photograph. The paper has become brittle and split. Photograph courtesy of Artlab Australia, reproduced with permission of Mortlock Library, State Library of South Australia

The worst reaction for historic black-and-white photographic prints on paper is the photochemical breakdown of lignin, contained in some papers. This reaction produces peroxides, which are strong oxidising agents and chemically attack the silver image.

Exposure to light can multiply the adverse effects of poor environmental conditions. Remember that damage caused by light is often accelerated by high relative humidity and temperature.

Ideal conditions for the display of photographs

Photographs should be displayed in similar conditions to those outlined for their storage; however, there are some differences.

Light is essential in a display environment, but must be set at levels which will not adversely affect the collection. Original historic photographs and colour prints should be considered sensitive to light. Therefore:

• the brightness of the light should be less than 50 lux; and

• the UV content of light should be less than 30µW/lm and no greater than 75µW/lm.

Copy photographs and Cibachromes can be illuminated at higher levels.

The ideal storage temperature for photographs is quite low and is often thought to be too cold for the comfort of people visiting or working in the museum, gallery or library. Therefore the compromise temperature for the display of photographs has been set at 21ºC.

Relative humidity is in the moderate range of 30–50%RH, with fluctuations kept to a minimum, as for storage.

The control of relative humidity in a display area may be more difficult than in a storage area. Fluctuations in relative humidity are more likely, because of the varying numbers of people visiting the display followed by no people at times when the display is closed.

The emphasis should be on providing a buffer zone between the photographs and the extreme or fluctuating conditions. Display cases and frames provide layers of protection from extreme or fluctuating conditions.

Protect photographs on display from pollutants, dust and insects.

It is important to use appropriate materials and methods when displaying photographs: to ensure the long-term preservation of the collections.

Lighting hints

Photographs are made up of a number of different materials, and lighting levels for display must take into account all those materials. This is why most photographs are considered to be sensitive to light.

As light can be so damaging to photographs it is important to consider carefully the lighting of displays. This section provides some hints of how to minimise damage to items lit for display.

Tungsten incandescent bulbs are the best form of lighting for the display of photographs because they give out very little UV radiation.

Keep the brightness or intensity of the light low, and regulate exposure periods. Less exposure to visible light and the elimination of UV radiation helps prolong the life of photographs.

When displaying photographs, remember that light also affects the paper on which the photographs are printed—except for particular types of photographs such as opaltypes, which are on glass. Single-layer and two-layer photographs should be displayed in lower lighting levels than those with a three-layer structure. The baryta layer in the three-layer structure protects the paper support and there is less likelihood of photochemical damage to the paper.

Never display original salted paper prints. They are extremely light-sensitive and can fade badly.

It is recommended that copies be displayed, rather than the originals.

Framing and mounting photographs for display

Mounting and framing photographs supports and protects them from extreme or fluctuating environmental conditions, as well as enhancing their appearance.

Mounts/mats

Window mounts/mats prevent direct contact between the surface of the photograph and the glazing. They are also used for aesthetic reasons, providing a border for the image.

It is important to separate the glazing from the photograph because:

• sudden temperature changes can cause condensation on the inner surface of glass;

• if the photograph does not have a window mount, the emulsion can become sticky and stick to the glass; and

• if photographs stick to glass and then dry off, they are extremely difficult and sometimes impossible to separate without damaging the image.

Photographs should be hinged and mounted in the same way as works on flat paper.

If there is enough margin at the edge of the photograph, you can use photocorners to attach the photograph to the mount. This will be easier with modern, colour photographs because many water-based adhesives will not stick easily to resin-coated paper.

If you don't have the equipment to cut window mounts, contact your local framer, who should be able to cut the window for you.

If you are having items mounted and framed by a framer, specify conservation mounting and framing and conservation-grade materials. Not all framers have conservation-grade materials in stock, so give them enough time to order the materials in.

If you would prefer not to have a window mount/mat framing the image, some provision should be made to separate the photograph from the glazing once it is framed. This is usually done with spacers. These can be made with strips of mount board stuck to the inside of the rebate of the frame. They should be cut thin so that they are not visible.

Frames

Frames add to the aesthetic appeal of photographs and provide a solid, protective outer layer for the photographs they contain. This is particularly important if you are dealing with a travelling exhibition; in this case the frames are not only protective but are also much easier to handle than unframed photographs.

Conservation framing is more complex and more expensive than standard framing techniques, but it is the best protection for your collection while it is on display, especially if the photographs are to stay framed for a long time and are part of a travelling exhibition.

There are a number of components in the conservation framing system.

Click here to see Diagram

The moulding is usually referred to as the frame. Different types of framing materials will be discussed further in the section The best materials to use for the display of photographs.

Glazing should provide physical protection to the photograph with a minimum of distraction to viewing. Glass or acrylic sheeting can be used for glazing. Each has advantages and disadvantages:

• glass can break and damage the photograph. It has a slight colour, either a blue or green, which may interfere with the colour-balance in the photograph. This colour becomes more noticeable as the glass ages; and

• acrylic sheeting, such as Perspex or Plexiglas, is prone to scratching, which can be visually disturbing. It can also develop a strong static charge. But acrylic sheeting gives better protection against UV radiation than glass, particularly if a UV-absorbing acrylic is used.

The glazing seal—shown as a rightangle in the diagram—is applied around the edges of the glazing to the rebate of the frame. It stops insects and airborne pollutants from entering through the front of the frame. It also protects the photograph from any chips of glass which may come away from the cut edge of the glass.

Glazing seals are not used universally in conservation framing systems-some argue that they reduce the rate of air interchange between the frame and the outside world.

The moisture barrier—an inert material—for example, Mylar or aluminium foil attached at the back of the frame, reduces moisture migration into the frame. Creating this barrier is important when framing items which are particularly sensitive to moisture: Cibachromes, for example. The moisture barrier is shown between the brad and the gummed paper tape.

The outer tape seal, from the edge of the moisture barrier to the edge of the frame, completely seals the package and stops insects and air pollutants entering the framing system.

Easy do-it-yourself methods for displaying photographs

It is not always appropriate to go to the expense and effort to frame your photographs for display, especially if they are to be displayed only for a short time. But it is still important to provide protection and support for the photographs. Some alternatives to mounting/matting and framing are:

• displaying your photographs in their polyester or polypropylene storage sleeves; and

• placing the photographs in their storage sleeves in a mount.

With these two methods, you can place the photographs in a display case or attach them to a display board. When attaching them to a display board, make sure:

• the method of fixing the items to the board is secure and will not allow the photographs to fall; and

• it must not damage the photographs or their permanent storage enclosure. For example, pushing pins through the storage sleeves is not recommended, while using double-sided tape on the outside of the storage sleeves would not cause any lasting damage and would be easy to remove if the exhibition was a short one.

When attaching the photographs to a solid support, such as a sheet of conservation mount board cut to an appropriate size, the methods described in the section on storage can be used. Once the photograph is supported adequately, it can be placed in a display case. The solid support performs a number of functions:

• it supports the photograph during handling, that is, when it is being placed in or removed from the display case; and

• it acts as a barrier between the materials of the display case and the photograph.

The best materials to use for displaying photographs

As already discussed in the section on storage, some materials can have an adverse effect on photographs. It is important to select carefully the materials which you are going to use in your display system.

Wrappers, enclosures, mounts and anything which is in direct contact with the photographs should be made from materials that are chemically inert and which will not cause physical damage to the photographs.

Mount/matboard should be conservation-grade: either a 100% rag board or purified wood-pulp-alpha cellulose. These boards have had the lignin and other contaminants removed.

Black-and-white gelatine emulsion photographs can be mounted/matted with board which has a 2% alkaline buffering. Whether a board is buffered or not will be noted in the manufacturer's specification.

Colour prints and cyanotypes should not be mounted on boards which contain alkaline buffers; a photographic-quality mount/mat board would be suitable for these photographs.

The two most common framing materials are metal and wood.

Metal frames—aluminium section—are ideal for framing photographs because they are:

• physically strong;

• chemically inert, giving off no destructive vapours;

• unaffected by decay, insect or fungal attack;

• the assembly hardware allows them to be opened easily for inspection; and

• the clean, simple mouldings present most photographs to their best advantage.

Wooden frames often look very impressive, especially on historic photographs. But they have characteristics which could make them unsuitable on preservation grounds:

• raw wood gives off peroxides, which are strong oxidising agents and harmful to prints; and

• softwoods, like pine and cedar, contain resins which remain volatile for years and will affect prints adversely.

Basswood and Jelutone are low-resin woods and are considered suitable for preservation-grade frames.

If you are using wooden frames, the rebate should be sealed with polyurethane or acrylic resin varnish to prevent acid vapours from the resins reaching the prints. And remember that even hardwoods contain some resins.

Frames which have been sealed as outlined above, stained or painted should never be used until the paint has cured thoroughly. Dry, but uncured, paint emits vapours known to be particularly harmful to photographic emulsions.

Tapes suitable for use as glazing seals are Filmoplast P90, Tyvek tape, 3M Scotch 810 magic transparent tape and polyester tape 8411.

Tapes suitable for use as outer seal tapes are gummed paper tape, Tyvek tape, 3M Scotch 810 magic transparent tape and polyester tape 8411.

Mylar is suitable for use as a moisture barrier in a conservation framing system and as a storage and display sleeve.

Polypropylene can be used as a display sleeve; but it is not as clear as Mylar and does not look as attractive.