PMG Section 1.6 Exhibition Techniques for Photographic Material

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Photographic Materials Conservation Catalog
Chapter 1 - Exhibition Guidelines for Photographic Materials

Date: July 2004
Compiler: Stephanie Watkins, 1993-2004
Initiator: Douglas Severson, 1992-1993
Contributors (Alphabetical):
Catherine Ackerman, Nancy Ash, Sarah Bertalan, Jean-Louis Bigourdan, Barbara N. Brown, Ed Buffaloe, Carol Crawford, Corinne Dune, Thomas M. Edmondson, Debra Evans, Julia Fenn, Betty Fiske, Gwenola Furic, Judy Greenfield, Doris Hamburg, Marc Harnly, Pamela Hatchfield, Cathy Henderson, Nancy Heugh, Ana Hofmann, Emily Klayman Jacobson, Martin Jurgens, Nora Kennedy, Daria Keynan, Lyn Koehnline, Barbara Lemmen, Holly Maxson, Constance McCabe, John McElhone, Cecile Mear, Jennifer Jae Mentzer, Jesse Munn, Rachel Mustalish, Douglas Nishimura, Leslie Paisley, Sylvie Penichon, Hugh Phibbs, Dr. Boris Pretzel, Dr. Chandra Reedy, Nancy Reinhold, Andrew Robb, Grant Romer, Kimberly Schenck, Douglas Severson, Tracey Shields, Angela Thompson, Sarah Wagner, Clara Waldthausen, Dr. Mike Ware, Stephanie Watkins, Dr. Paul Whitmore, Faith Zieske, Edward Zinn.

First edition copyright: 2004. The Photographic Materials Conservation Catalog is a publication of the Photographic Materials Group of the American Institute for Conservation of Historic and Artistic Works. The Photographic Materials Conservation Catalog is published as a convenience for the members of the Photographic Materials Group. Publication does not endorse nor recommend any treatments, methods, or techniques described herein.

1.6. Exhibition Techniques for Photographic Materials

1.6.1 Perceptual adjustments
Human brains perceive color in light and adjust to available light. Understanding how the human brain and eye process photons can be helpful when designing lighting. The optimal blend is safe light levels for preservation and sufficient light levels for color rendition.

1.6.1.1 Using lighting situations
Different types of bulbs (e.g. tungsten, fluorescent, etc.) produce different spectral energy distributions. It is important to choose a bulb that emits low levels of the wavelengths that are most damaging to the types of photographs being displayed. For example, low­UV-emitting bulbs are available. "Color temperature specifies only the color and saturation of the light. There are many spectral energy distributions which yield the same color temperature." (Brill, 1980, 18) The interaction of color temperature and footcandles (lux) is also deserving of consideration. Higher wattage bulbs produce more footcandles (lux), thereby causing more damage. The human eye will tend to perceive lower levels of illumination as balanced "white" illuminance even if the light is "warmer", that is to mean, at a lower color temperature. The infrared output needs to be monitored as lighting becomes warmer. While most people prefer warm lighting situations, Lull's (1999) experience indicates that cool lighting can be offset with warm tungsten light sources to balance the exhibit space without substantially increasing the footcandle (lux) output, yet making the exhibit area easier on the eye. Placing the lighting units as far away from the photograph as possible will reduce the impact of heat. Exhibition lighting for photographic materials should only be turned on when it is needed, thus limiting the exposure time for the items on display. Reilly (1986, 105) notes, "people coming from outdoors or a brightly-lighted part of a building need up to several minutes to fully adapt to low levels of illumination. Adaptation may be encouraged by routing visitors who are approaching the exhibition area through rooms and corridors with successively lower light levels." Once in the darkened room, it is advised to direct illumination to the vicinity of the hung item. Reilly (1986, 105-6) additionally recommends illuminating the exhibition area evenly and avoiding very light or very dark walls. Bouncing lighting off a white ceiling can evenly illuminate a smaller, darkly painted exhibition room. Not all exhibition spaces are restricted for viewing purposes. Ritzenthaler et al. (1984, 128) notes that light levels could be lowered substantially without affecting other activities for exhibits in reception areas or reading rooms. She and her co-authors also suggest, "notes posted in exhibition areas explaining the reasons for reduced light levels will help to generate understanding and support on the part of the visitors."

1.6.1.2 Using wall and mat colors
Increasingly darker shades of wall colors (e.g., going from brilliant white to a medium gray) can be used in conjunction with successively decreased illumination to provide for low light levels. Small or "intimate" exhibition spaces with low light levels can appear more inviting by using wall colors with warm undertones, which are more soothing and relaxing on a subliminal level. Wilhelm additionally notes (1993, 610) that "dark or black walls and ceilings should be avoided since most people do not like the 'cave' feeling of darkly painted rooms." A light-colored ceiling will make a room appear brighter and larger (see section 1.6.1.1). Light-colored mats against dark frames set against darker wall colors will "spotlight" pictures. Wilhelm notes (1993, 610) that the "visual appearance of the photograph is enhanced when the surrounding areas are darker than the photograph."

1.6.1.3 Reducing glare
Picture glazing and glossy wall paints can reflect spotlights intensely, producing viewer eyestrain. The use of neutral density glass, acrylic sheeting, or antireflective glass can help make dark photographs with glossy surfaces easier to see. Wilhelm (1993, 610) advises avoiding white or light-colored walls "since the bright surfaces will have the effect of reducing the apparent brightness of the print and will increase glare on the glass over photographs on opposite walls." Anti-reflective (AR) glass can help make a dark photograph with a glossy surface easier to see. Sunlight and "other sources of bright light should be eliminated in photographic display areas," advises Wilhelm (1993, 612) as "uneven lighting and difficult viewing conditions are created during daytime hours." The varying, unregulated light levels can also significantly increase the footcandle (lux) and ultraviolet level. When windows cannot be avoided, Wilhelm advises reducing the ultraviolet radiation through windows by using ultraviolet filters such as Lucite® SAR UF-3 or Plexiglas® UF-3.

1.6.2 Display techniques to reduce light exposure
1.6.2.1 Covered frames and cases
Veils, curtains, drapes, and shrouds can be constructed out of opaque, dense-weave, light­obstructing fabrics such as heavy twill, velvet, or velveteen. Doubling the fabric or backing the cloth with Tyvex® or a similar material provides additional shading of the object. When lifted for viewing, a dark-colored liner will reduce glare. Cloths can be weighted with a rod or bar (e.g., Plexiglas®), light drapery weights, or fishing weights as appropriate to ensure coverage of the photograph and to facilitate easy lifting of the cloth, but also may increase the likelihood of being left open by visitors. Advanced designs can incorporate pull cords to open and close a protective cloth or drape. Designs should allow for easy access for visitors in wheelchairs. Shadow box construction can help support a protective cloth and provide additional shade from ambient light from the edges. Costs include fabrics, weights, perhaps cords, and labor for construction, making this a potentially inexpensive, yet effective option for reducing light exposure.

1.6.2.2 Closed cases
Drawers have been used to house and display photographs. Care must be taken to ensure that the photographs are secure inside the drawer so that the motion of opening and closing the drawer does not scratch, jar, or otherwise adversely affect the photograph. Design of smoothly operating drawer runners that pull out flat (do not tip), have stops (so the drawers cannot be removed by visitors), and have adequate bumpers (to reduce jarring) is essential toward this end. Lighting for display cases must be chosen carefully. Many light fixtures and ballasts give off considerable heat and should not be located near photographic material. One alternative is to design an isolated lighting chamber lined with heat-reflecting glass and double-glazing (Raphael 1991, 12). An alternative to conventional lighting design that has lower heat and ultraviolet output is fiber optic systems.

1.6.2.3 Metal screening and neutral density filters
Metal screening and neutral density filters placed directly in front of the illumination source reduce the light intensity (see section 1.5.2).

1.6.2.4 Dimmers
Thomson (1986, 207) notes that dimmers are energy efficient because they "use phase control circuits which alter the phase between current and voltage." However, for photographic materials, Wilhelm (1993, 609) notes the limitations of dimmers beyond "making minor adjustments in light intensity." They "should be used with restraint, since the color temperature of the light is lowered, and the light becomes progressively redder (increasing infrared output), as the light intensity is reduced below normal. Low-voltage lamps operated by a transformer require special types of dimmers, and quartz halogen lamps cannot be dimmed beyond a certain point wihJ,out interfering with the halogen cycle." The amount of ultraviolet light that can be reduced will vary depending on the type and original spectral output of the bulb being dimmed. The costs vary by brand and quality but are comparable to timers and motion detectors.

1.6.2.5 Timers
Timers provide illumination as needed through viewer activation of switches or push buttons that thereby limit the exposure times for an item. Timers are energy efficient if tungsten light sources are used. In heavily attended exhibitions the lights end up being on much of the display time, although less than normal. In many museums, the gallery lights are turned on to allow for security, maintenance, and janitorial functions for many more hours than those open to the public. Diagrams instead of written instructions are beneficial for visitors who do not read the local language. Location of devices for activating the timers should be set at levels that can be activated by visitors in wheelchairs. The costs vary by brand and quality but are comparable to dimmers and motion detectors.

1.6.2.6 Motion detection, occupancy sensors, or "light on demand"
Motion detectors provide lighting as needed without the public having to manipulate switches or read or interpret directions. A darkened gallery may be interpreted by many as a closed gallery, however. Signage at the gallery entrance is recommended to welcome visitors and briefly explain the lighting. Additionally, they meet access standards set by the American with Disabilities Act (USA). They are ideal for energy efficiency and restricting the period of light exposure to an item. However, in large exhibitions, the lights will be on much of the display time. The detectors can also provide an impromptu game for children, though attentive guards should be able to reduce unnecessary use of this kind. Motion detectors can be purchased in conjunction with timers. The costs vary by brand and quality but are comparable to timers and dimmers.

1.6.3 Lighting techniques for objects
1.6.3.1 Transmitted light illumination
Viewer-activated light boxes can be used for sensitive or transparent material, such as waxed, salted paper negatives, thereby limiting light exposure. Viewer-operated fiber optic mats have been used to illuminate wax paper negatives and transparencies from the reverse.

1.6.3.2 Double-sided images
Poly (ethylene terephthalate) (MYLAR® Type D, Melinex® 516) encapsulates and double-sided mats and frames have been used to support items during illumination. Freestanding plinths and false walls built perpendicular to primary walls (along with two-sided frames and window openings) are useful for viewing translucent or double-sided images. They can be illuminated from one side or by reflected light from below.

1.6.3.3 Daguerreotypes
Daguerreotypes are best viewed with "single-source" directional light illumination coming from a 45° angle to the place surface. This arrangement will allow the reflected light to pass to the side of the viewer; otherwise only glare or a mirror effect will be seen. Overhead illumination descending across the horizontally oriented polish plate marks will create a haze of scattered light that can obscure much of the image.

1.6.4 Security techniques
Nineteenth-century photographic formats, such as daguerreotypes, ambrotypes (positive collodionst tintypes, and cartes de visite (CDV) are often small. Added care should be taken to ensure that these materials are mounted securely, displayed in cases, or otherwise secured against the possibility of theft. Exhibit cases should have locks or barrier devices to prevent unauthorized access. Frames can be secured to the wall to reduce damage from theft or minor earthquake. Large, oversize contemporary photographic materials may be collage composites or composed of easily scratched materials (e.g., plastics). Real and psychological barriers such as platforms, floor wedges, and protrusions can be used in the display area to restrict public access to the surface of photographs when glazing is not practical or conflicts with the photographer's intent.

1.6.5 Rotation, replacement, duplication, and facsimiles
1.6.5.1 Using rotation, facsimiles, and duplicates
Similar objects can be used in rotation when use of the original is a necessity. For didactic or historical purposes, it may be wise to use facsimiles or copies, especially when an image is being used for its information, rather than its artifactual value or when exposure conditions cannot be controlled to preclude damage. Facsimiles should also be used if security is limited. Wilhelm (1993, 241) believes that "facsimile color copies should be made before a fading or staining limit is reached." Facsimiles of album pages can be made in order to display several images from the album at once. With any methodology used in creating a facsimile, it is essential to clearly and permanently label the facsimile as such. Some types of photographic facsimiles can be made commercially by local businesses such as copier, graphics, or aerial photographers (check with local or regional highway departments). Prepare the original material for reproduction by providing a rigid backboard and sleeve or encapsulation of the material in polyester film. (Potential glare from the polyester film can cause difficulty for the photographer, unfortunately.) Stay with the materials while the order is being processed. Carefully consider the risks posed to rare, important, or vintage prints when commercial firms handle them. Also, consider that photocopying processes can cause damage from light exposure or handling.

1.6.5.2 Types of reproductions
Authentic historical methods can be used to fabricate new examples. For example, salted paper prints can be newly made. Modern materials can sometimes be used to create convincing substitutes. For example, autochromes can be reproduced by color transparencies using a digitized color-analyzing system. Facsimiles of most photographic processes, complete with replication of the damage or aging effects, can be successfully made. Duplication processes currently available can produce good-quality facsimiles with relatively good light stability. This technology is rapidly changing, and the development of alternative techniques is inevitable. Please consult current printed sources and websites.

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