Protection from Lighting DamageWhen we think of light damage, we think of fading, but fading is only the most recognizable form of damage.Light is a very common cause of damage to collections. Many materials are particularly sensitive to light: paper, cloth, leather, photographs, and media (inks, colorants, dyes, and many other materials used to create objects and art). Aside from fading, there may be damage to the physical and chemical structure of materials. Light and ultraviolet radiation (UV) provides energy to fuel the chemical reactions that lead to deterioration and while UV is blamed for most of this damage, visible light is also problematic.Intensity and long exposure times can lead to fading or changing colors in dyes and colorants. Ultraviolet radiation will lead to weakening, bleaching, and yellowing of paper and other organic materials. All of these changes can diminish readability, affect the aesthetic appreciation of artwork, and impact access to the information contained therein. Even if you take a faded photograph down and store it in the dark, it will not return to its original appearance and will continue to fade when taken out again.Because this damage is cumulative andirreversible, it is important to understand how to protect materials in the first place.THE NATURE OF LIGHTElectromagnetic Spectrum

Light is the band of radiation that allows us to perceive color and is composed of many different wavelengths that correspond to specific colors. Bookending the visible light spectrum is ultraviolet (UV) and infrared (IR) radiation. Neither UV nor IR is visible, but they are damaging: UV radiation will yellow and weaken materials and IR will cause the surface of objects to heat up. The visible spectrum and UV radiation are of greatest importance for preservation.The visible spectrum runs from about 740 nanometers (nm is the form of measurement applied to radiation) to about 380 nm. Ultraviolet radiation lies just below the short end of the visible spectrum (below 380 nm) and infrared (IR) radiation lies just above the long end, but their existence does not affect how our eyes perceive color.There are two ways we can measure how the human eye responds to light: Color Rendering Index (CRI) and Color Temperature (CT). CRI measures on a scale from zero to 100 light quality in relation to the eyes ability to see colors correctly. There is no standard for an acceptable CRI but museum lighting designers suggest 80 - 100 to ensure colors can be viewed properly. Daylight falls at 100 on the CRI scale while many compact fluorescent lamps (the industry term for bulbs) are near 80 and LEDs, while variable, can read as high as 90.Color Temperature measures the quality of light from cool to warm in units of degrees Kelvin (K). CT can be somewhat confusing since warm lightusually referred to in relation toGOLDto red toneshas a lower CT than cool light, usually referred to in relation to blue tones. Because fluorescent lamps and LEDs come in a wide range of color temperatures, be sure to check the specifications for each lamp you are considering. Cooler light (3500-5000K) will increase the contrast of objects, which may be desirable but may also alter the appearance of the object. Because of this, warm light (2800K) is preferred by the museum community (when the lux levels are low).MEASURING LIGHT LEVELSVisible light levels are measured by a light meter in lux or foot-candles. Lux, simply stated, is the measure of the intensity of light over one square meter. A foot-candle, the old imperial measurement of light intensity, equals about 11 lux. To get the most accurate measure, the meter should be placed where the object will be located and situated just as the object will be when it is on display.UV meter

In general, light meters only measure visible light; to measure the proportion of UV radiation in light, a UV meter must be used. UV meters, however, can be expensive: if a meter is not available, it is best to assume that sunlight, fluorescent lamps, and quartz-halogen lamps will read above the recommended maximum of 75 W/lm (microwatts per lumen) and that displays in this light will require filtering. Manufacturers information is available about UV emissions for the various lamps that are on the market: checking the manufacturers website will generally provide you with the specific information you need.If no light or UV meter is available, it is possible to estimate the damage that might result to an artifact from particular intensities of light and lengths of exposure. This can be done using the ISOs Blue Wool standard cards, available from a number of conservation suppliers.More than other measurements, the Blue Wool cards visibly demonstrate the destructive powers of light. Because these cards provide a standard against which subsequent fading can be judged, they can be used to convince skeptics that light really is a problem. Each Blue Wool standard contains eight samples of blue-dyed wool. Sample 1 is extremely light sensitive, while sample 8 is the most stable dye available (although not permanent). Sample 2 takes twice as long to fade as sample 1, sample 3 takes twice as long as sample 2, and so forth. For more information, see Light, Ultraviolet and Infrared by Stephan Michalski in Resources.To demonstrate the degree of fading caused by the intensity of light in a particular location, cover half of the card with a light-blocking material to protect it completely from light damage (or cut the card up into strips reserving one as a control). Note the date and set out the Blue Wools in the desired location. Check periodically (every couple of weeks) to determine how long it takes the various samples to fade. Since the sensitivity of the first few samples on the card corresponds to light sensitive materials such as watercolors and textiles, the results will give you a general idea of the amount of damage you might expect if materials were exhibited for the same period of time at the current light level in that location.In most cases, a general correlation between the sensitivity of the artifact and the Blue Wool standard's scale will be sufficient to allow informed decision-making.Blue Wool Card

SOURCES OF LIGHTThere are two sources of light: sunlight and electrically produced light. As a primary light source, sunlight is not recommended. It is too intense, causes extensive fading, and has a high UV component, which also causes damage at the chemical level. Different types of electrical lighting may be required for storage, staff, public, and exhibition spaces within libraries, museums, and archives. It is helpful to understand the available options and characteristics to select the best option for lighting these spaces. The most common lamps found, especially in storage and exhibit spaces, are:caption

Incandescent lamps Tungsten lampsproduce light when an electric current is passed through a tungsten filament. These lamps convert only a small percentage of the electrical current into light; the rest is given off as heat. The traditional tungsten lamp is being phased out and will be difficult to obtain after 2014. Quartz tungsten-halogen lampsare a variation on the traditional incandescent lamp; they contain halogen gas inside a quartz bulb, which allows the light to burn brighter and longer. Quartz tungsten-halogen lamps are often used in exhibition lighting; examples include the Halogen Parabolic Aluminized Reflector (PAR) and the Multifaceted-Reflector (MR) lamps. These lamps give a very good light spectrum overall but emit a lot of heat. The casings get very hot, and the lamps have been known to explode. Fluorescent lampscontain mercury vapor inside a tubular glass lamp whose inside surface is painted with white fluorescent powder. The lamp can come as a tube in multiple lengths and diameters, in compact tubes (CFT), and in various shapes to screw into traditional incandescent fixtures (CFL). Fluorescent lamps are inexpensive to use but the commonly available versions emit significant UV radiation. Manufacturers do make low UV versions of all of these lamps so check the manufacturers website for accurate information on specific lamps. Light Emitting Diodes (LEDs)are semiconductor devices (materials with electrical conductivity) that can emit a specific spectrum (color temperature) of light depending on the semiconductor material used. LEDs do not emit UV or IR radiation and the light does not generate heat (although the conductor box does). They can supply light for a lower energy cost and have a longer lifespan than other light sources. There is a wide variance in color temperature and CRI and the intensity of the light can diminish over time.For more information on lamps for libraries, archives, and museum spaces, see Michalski, Light, Ultraviolet and Infrared.Light damage to leather binding

CONTROLLING LIGHT DAMAGEMolecules, the basic chemical building block of all materials, are in constant motion. On the electromagnetic spectrum, as the wavelengths get shorter, thepotential energy increases. When this energy is introduced to the molecules, they vibrate more quickly (they get excited) and begin to spread out. Thus, wavelengths that are short (e.g., those from the ultraviolet portion of the spectrum) will increase the vibration of the molecules and encourage them to expand, then cleave, and bond again, which leads to the deterioration of plant and animal fibers. In addition, this re-bonding can change the way that visible light interacts with the material, causing a change in the wavelength of the light and, as a result, we are shown a different color. For example, a book with a dyed leather cover sits in the sunlight at the end of a shelf, over time, the light causes the molecules in the dye to vibrate more quickly, bump into each other like a demolition derby, and change their shape. The light hitting and reflecting off these new molecules changes the speed of the wavelength and thus the color the eye perceives in relation to the dye changes. The general term for this process is photochemical deterioration.Along with fading, another of the primary photochemical reactions is oxidation, in which the excited molecule transfers its energy to an oxygen molecule, which then attracts other molecules to initiate damaging chemical changes including embrittlement and yellowing. While the reactions can be extremely complex, the result is always deterioration.As wavelengths become longertoward the infrared end of the spectrumthey have less energy and reduced capacity to excite molecules. However, the energy absorbed from infrared radiation can increase an object's temperature. High temperatures are another form of energy that increases molecular vibrations and speeds up the damaging chemical reactions. For more information on temperature and its effect on collections, see NEDCC leaflet 2.1:Temperature, Relative Humidity, Light, and Air Quality: Basic Guidelines for Preservation.Since UV radiation is the most energetic, and thus the most destructive, it is easy to assume that if UV radiation is eliminated, damage will cease. Unfortunately, this is not the case; visible light also causes damage. While exposure to UV can be eliminated from exhibit and storage areas (and diminished in public spaces with filtering and lamp selection), reducing visible light requires different strategies.In storage areas, strategies to control the damage caused by light and UV radiation include: putting light sensitive items into boxes; keeping the lights off when no one is retrieving materials or installing motion sensors on the lights (this step also saves on electricity costs); filtering tubular fluorescent lights with UV blocking sleeves (no filters exist currently for compact fluorescents); and covering windows with shades.There are a number of ways to control light in combined storage and staff or public spaces: Cover windows and skylights with UV blocking film and shades which should be closed during the most intense light of the day. Filter tubular fluorescent lights with UV blocking sleeves (no filters exist currently for compact fluorescents). Keep collections off of top shelves and away from direct contact with windows. Protect any materials that may be particularly susceptible to light damage, such as framed color photographs or watercolors, by displaying away from any direct light (sunlight and spotlights) and glazing with UV blocking glass or Plexiglas or by displaying good quality facsimiles. Keep lights off when spaces are not occupied, especially after hours.Filtering Ultraviolet RadiationAs mentioned, UV radiation can be filtered. UV-filtering films for windows, exhibit cases, glass fronted cabinets, etc., are flexible and adhere to glass, acrylic, or polycarbonate. Filters vary in the wavelengths of UV radiation they block, as well as the amount they are able to block. Filters can be clear or tinted (filtering visible light as well) and many can act as insulation from solar heat gain. UV-filtering film is most effective if it covers the surface it is placed on completely so that all light passes through it. For information on acceptable window films and how they age, as well as many helpful charts of the different manufacturers films, see UV-Blocking Window Films for Use in Museums Revisited in the Western Association for Art Conservation (WAAC) Newsletter, listed in the Resources.If film is not an option, acrylic panels that have built in UV blocking capabilities can be used. The acrylic can be used: in place of window glass (if fire regulations allow); mounted as secondary glazing on existing windows; or mounted inside the window from hooks, magnets, or a separate frame (the panel must be cut larger than the window glass, so that all light passes through it).Filters for tube-shaped fluorescent lamps are available in the form of soft, thin plastic sleeves and hard plastic tubes. Filters are not yet available for non-tubular fluorescent lamps. While the hard plastic tubes are generally much more expensive than the thin sleeves, they are also much less likely to be accidentally discarded with the old bulb, as they are more conspicuous. Both filters should fit the tubes but, if necessary, two thin sleeves can be overlapped to form a longer sleeve for oversize fluorescent tubes. No specific guidelines exist for when to change these filters, but their useful lifetime ranges between 5-10 years.Some fluorescent lamps produce less UV than others. If a low-UV fluorescent lamp is chosen (check the product literature for UV emissions in microwatts per lumen), UV filters may not be necessary, but would be an added benefit.If fluorescent lights are housed in fixtures completely covered by a plastic shield (no open holes), sleeves may not be required for the lamps. The plastic shields often provide a moderate level of UV filtering but if the fixtures are in storage areas with unboxed collections materials, a layer of UV blocking polyester film on the inside will help improve filtering.EXHIBITION LIGHTINGWhile on exhibit, collections are most susceptible to light damage and care should be taken to protect these materials. The intensity of light and the length of time the materials will be on display are the primary factors and need to be considered together.Most collection materials can be on exhibit for three to four months at 50 to 150 lux and show no fading. A level of 50 lux is similar to the lighting in a home living room in the evening. For comparison, standard office lighting is around 400 lux and direct sunlight measures 30,000 lux. Lower light levels are necessary for light-sensitive materials such as watercolors, photographs, leather, textiles, and prints. Materials without color (printed text, black and white photographs, carbon black ink manuscripts, etc.) can be exhibited at up to 150 lux. It is acceptable to adjust the intensity of light up or down within this range depending on the sensitivity of materials. Very sensitive or fragile materials should be displayed with care or only displayed as facsimiles. No paper, wood, leather, textile, or other organic object should ever be on permanent display.If the light levels are to be higher than 50-150 lux, the length of time on exhibit needs to be decreased accordingly. When making the decision about time on exhibit and light levels, be aware that low light levels for extended periods of time cause as much damage as high light levels for short periods. We can measure the damage to materials in direct proportion to the light level multiplied by the time of exposure, measured in lux hours (lx h). For example, an object lit for 10 hours a day at 50 lux for 100 days would have a light dosage of 50,000 lx h. Ideally, light-sensitive materials would only have an annual exposure of 50,000 lx h, regardless of whether they will be displayed annually or not. When considering how much and how often an item is to be on display, always keep in mind that light damage is cumulative and irreversible.Using lux hours to track light exposure provides useful and concrete information on how bright exhibition lighting can be by clearly showing that the same amount of expected damage occurs with brighter light and short time as dimmer light and long time. In order to use this principle effectively, good records of exhibition durations and actual light levels must be kept.Ultimately, every institution must decide on an acceptable upper limit of exposure (i.e., a certain number of lux hours per year) for exhibited objects, which may differ for different parts of the institution's collection. When establishing limits on exhibition times, factors to consider include: the amount of time the lights are turned on in the exhibit space (this figure is not always as straightforward as simply noting exhibition hours, since lights are often turned on for housekeeping or other purposes when the exhibit is closed to the public); the sensitivity of the items being exhibited; the desired lifespan of these items; the levels requested by a loaning institution; and the importance of aesthetic concerns in exhibition.Finally, where possible, spotlights should not be trained directly on an object; if spotlights are necessary, appropriate filters must be used. Indirect and low lighting will spare the object, and will require less adjustment of the eye from areas of intense light to those of relative darkness, allowing the use of lamps with a lower wattage throughout exhibit spaces.Labels explaining the reason for low light levels in the exhibit can be used to educate visitors and actually increase their understanding of the value of the collection.CONCLUSIONAll light is energy and the energy that light provides fuels destructive chemical reactions that contribute to the deterioration of collections in libraries, archives, and museums. Light also damages bindings, photographic emulsions, and other media, including the inks, dyes, and pigments used in many library and archival materials.While all sources of ultraviolet light should be filtered, and the exposure of collections to visible light should be strictly controlled, the guidelines in this leaflet will allow institutions to take these factors together and make informed decisions reconciling the needs of their collections and their exhibitions.

RESOURCESBoye, Colleen, Frank Preusser and Terry Schaeffer.UV-Blocking Window Films for Use in Museums Revisited.Western Association for Art Conservation (WAAC) Newsletter32, no. 1 (January 2010): 13-18.http://cool.conservation-us.org/ waac/wn/wn32/wn32-1/wn32-104.pdf.Druzik, James.Illuminating Alternatives: Research in Museum Lighting,Getty Conservation Institute Newsletter19, no. 1 (Spring 2004).http://www.getty.edu/conservation/ publications_resources/newsletters/19_1/news_in_cons1.html.Feller, Robert L.The Deteriorating Effect of Light on Museum Objects. Museum News Technical Supplement No. 3. Washington, DC: American Association of Museums, June 1964.Lull, William P, with the assistance of Paul N. Banks.Conservation Environment Guidelines for Libraries and Archives. Ottawa, ON: Canadian Council of Archives, 1995.Michalski, Stephan.Light, Ultraviolet and Infrared.Canadian Conservation Institute Caring for Collections. Last modified August 2, 2011.http://www.cci-icc.gc.ca/ caringfor-prendresoindes/articles/10agents/chap08-eng.aspx.Museum Exhibit Lighting, An Interdisciplinary Approach: Conservation, Design, and Technology.Proceedings of a workshop presented by the National Park Service and the American Institute for Conservation at the AIC Annual Meeting, 1997.Written by Donia Conn

Illuminating Alternatives: Research in Museum Lighting

By James DruzikThe last half of the 20th century saw the widespread acceptance and application of environmental guidelines designed to protect museum collections. In recent decades, these guidelineswhich delineate standards for temperature, humidity, lighting, and other environmental factorshave provided unprecedented stability for the environments of many museums, reducing the danger of damage to objects in their collections. Guidelines exist to enforce consensus, codify experience, and distill large amounts of technical information into general practice, reproducible simplicity, and rational institutional policy. Yet for guidelines to remain vital and useful, they must be periodically scrutinized against evolving knowledge and changing practices. Without regular examination, guidelines suffer from a creeping obsolescence.Over the past decade, most preventive conservation guidelinesincluding those that apply to relative humidity (RH), temperature, and air pollution exposure limitshave been reviewed and, gratifyingly, have held up surprisingly well. These periodic reviews have resulted in increased flexibility in building operations and maintenance and in exhibitions display. At the same time, however, they often require greater attention to detail. Single and simple measurements are replaced with precise monitoring and record keeping.

The J. Paul Getty Museum exhibitionMichelangelo to Vasari: Drawing the Figure in Renaissance Florence. For sensitive works on papersuch as the old master drawings in this exhibitcurrent guidelines recommend limiting gallery illumination levels to 50 lux to optimize the display lifetime of the works. Photo: Rebecca Vera-Martinez, courtesy of the J. Paul Getty Museum.

If one chooses to operate near the limits of acceptable environmental standardsor is compelled to operate in this manner because of location in a historical buildingthe probability of damage to objects increases, making safe control a demanding occupation. Nevertheless, some researchers have developed a theoretical basis for suggesting that the risks can be managed consciously. For instance, at one time the limits for RH within a museum's environment were very narrow and ensured that no RH-induced damage was possibleat a significant financial cost, of course. However, theoretical and experimental groundwork has indicated that if the drift is slow enough, reasonable safety might be possible over a much wider RH range, so that a slow seasonal oscillation could replace rigid limits. In other words, while fast change is bad, slow change may not be so badit may even be acceptable.Museum LightingAnother area where risks can probably be more effectively managed is museum lighting. It has long been clearly understood that, over time, uncontrolled lighting leads to damage, including fading on objects. As a result, the means to control light through restrictive exposures was sought. Not too long ago, the ''law'' on illumination levels was strict and absolute. These exposure levels were deduced from a paucity of data, starting from about 1930, by several authors whose judgments were later reinforced by subsequent research. In 1961, when Garry Thomson, then scientific advisor at the National Gallery in London, suggested the now well-known illumination limits of 50/150/300 lux for objects of varying light sensitivity, he was actually averaging the recommendations of earlier researchers. In fact, 50 luxa dark environment indeedwill still fade light-sensitive colorants and effect other color changes if given ample time. Although present at the start, the question of how long 50 lux could be tolerated was not given the same emphasis it gets today. With current ideas of risk management gaining greater interest, conservators and curators have had to think about how much damage over how long a period of time is acceptable. Thus, preventive conservation lighting standards have undergone a slow revolution.Changes in thinking are also a result of changing technologies. One only needs to recall that fluorescent lamps had been commercially available for just 15 years before they were first suggestedin a 1953 International Council of Museums publicationas possible low-heat alternatives to incandescent lighting in some limited applications. No doubt they had been used before that time. Today we have many more lamp and fixture designs for track lighting, fiberoptics, and, perhaps soon, novel light-emitting diode (LED) alternatives.

Nancy Yocco, an associate paper conservator at the J. Paul Getty Museum, and James Druzik of the GCI examining an old master drawing from the Museum's collection. The information a conservation scientist provides on the materials used in old master drawings can inform a conservator's recommendations for exhibition lighting exposure levels for these works. Photo: Dennis Keeley.

Making lighting safer for sensitive artifacts at constant illumination has been the subject of recent study. In a demonstration project published in 2000 in theJournal of the American Institute for Conservation, Christopher Cuttle, now at the University of Auckland, used several 50-watt quartz-halogen lamps, filtered to the color-matching functions of the human eye, to approximate the color matching of unfiltered lighting. This research resulted in a major shift in envisioning museum lighting. Using three bands of colored light instead of one monochromatic light source reduced energy at certain wavelengths not essential for reasonable human visual color matching. As part of Cuttle's research, an assessment by 16 observers noted that the differences between standard quartz-halogen lighting at 50 lux and three-band filtered quartz-halogen at the same illumination were slight, yet the three-band lighting significantly reduced the energy delivered to the surface of the object. This type of lighting will probably inflict less photochemical damage at equal illumination and duration.Cuttle's promising research helped precipitate a two-day experts meeting on museum lighting at the Getty Center (seeConservation, vol.18, no.1). The meeting, hosted by the GCI in October 2002, addressed a series of questions involving the lighting of old master drawings. Participants came from Canada, England, New Zealand, and the United States. They included conservators, conservation scientists, curators, and lighting engineers.From the discussions at this meeting, it was evident that there were eight major lighting strategies that could improve the display lifetime of works of art on paper, such as old master drawings. Four of these strategies constitute the core of existing guidelines: reduce illumination levels of existing sources; interrupt illumination through the use of switches and motion detectors; remove ultraviolet and infrared radiation; and spread out exhibition display periods over many years, using assumptions about the most fugitive component to set total exposure amounts. (Monitoring actual color change on artifacts could be added to this core group, but it is quite rarely carried out in practice.)Beyond those four ideas are four other strategies that have thus far received less attention. These strategies include using new light sources such as LEDs with intrinsic three-band character; using filters designed to emulate the three-band concept on existing lamp architecture; investigating further the benefits of anoxic environments on reduced photochemical potential; and increasing the use of risk management methodologies with radiometric rather than photometric monitoring techniques. With input from the Getty Center meeting participants, the GCI decided to pursue these four possibilities as a set of activities that together define a research program.New StrategiesShepherding new light sources, such as LEDs, to destinations in museums, libraries, or galleriesalong with testing visitor response to new lightingwill be increasingly valuable. Well-designed visitor testing has benefits that include not only the evaluation of aesthetic appropriateness of a new light but also a chance to test sensitive issues like age-reduced viewer visual acuity at low illumination levels. The GCI will begin research and testing in this area at the end of 2004.A second activity for the research program capitalizes on the fact that the human eye is a poor judge of the relative energy of two equally bright but different sources. While the same object equally illuminated by daylight and incandescent light fades at different rates, the less destructive source may be as acceptable for viewing as the more destructive one. Thus, the strategy of retrofitting hardware like track-installed, quartz-halogen fixtures or fiberoptic illuminators to provide acceptable color rendering for the human eye at reduced overall irradiation (energy) can be pursued on two fronts. One front is to assemble filter packets from available products that achieve the desired goal; the other is to design a single glass filter and manufacture it. The former approach has the benefit of lower initial research costs and the potential for off-the-shelf filters with fewer long-term manufacturing support uncertainties. The latter approach can be more energy efficient and provide a closer match to the spectral reflectance characteristics of illuminated artifacts. The GCI is researching both frontsone with theLos Angeles County Museum of Art (LACMA), and the other under contract to the University of Texas, El Paso. It is anticipated that for both projects, external groups will verify that the filters achieve a reduction in light damage, all else being equal.The third strategy to achieve safer, longer display lifetime is to examine oxygen-free microenclosures, assessing their benefits and liabilities. Most, but not all, photochemically damaging processes involve oxygen in one of two fundamental ways. Remove oxygen and those paths are theoretically blockedand the absorbed energy is dissipated by a safer route. Unfortunately, oxygen is not always needed for photochemically damaging processes, and some important colorants used in artworks have been shown to be susceptible to change even in the absence of oxygen. Such anoxic light-induced change is termed photoreduction, and its extent in museum artifacts is not known. Nor is it known to what extent those photoreducing components can be detected in advance in individual objects, which can then be excluded from such environments. Clearly a large screening study is in order. Also needed are techniques to make the construction of atmosphere-controlled encapsulations practical and inexpensive at the level of individually framed works. Some of these techniques have been worked through at Tate Conservation Department in Britain, with support from the Liverhulme Trust. The GCI is in discussion with other institutions regarding systematic materials screening under anoxic atmospheres.Finally, considering altering the emission spectra of exhibition lighting or adopting new light sources altogether suggests that it is time to improve the basic manner in which light monitoring is carried out. In the past, conservators have been content with measuring lux or footcandles. For a variety of good reasons, this was an acceptable practice. But better management demands better tools. When the spectrum of an incandescent lamp is altered, measuring illumination based upon the human eye's sensitivity loses relevance. It would be best to measure the incident energy for the same perceived level of brightness. Energy units are not new in conservationspecifications based on the number of microwatts per lumen of allowable ultraviolet light have been around for as long as footcandles. But in the absence of a need, or a desire, to measure energy directly, rebuttable presumptions about energy levels have replaced direct measurements. The GCI and LACMA are pursuing this research into monitoring.With all of these research objectives in mind, the GCI, along with its partners, hopes ultimately to provide museums and libraries greater flexibility in extending the display lifetimes of their light-sensitive artifacts. This achievement, in turn, will better facilitate all the functions of modern museums, whose stewardship calls on them to preserve, display, and educate.James Druzik is a senior project specialist in the Science department of the Getty Conservation Institute.

IntroductionThis report analyzes the lighting qualities in three San Francisco Bay area museums; the San Francisco Museum of Modern Art and the Yerba Buena Center for the Arts in San Francisco, and the University Art Museum in Berkeley.

View of the bridge and skylight at the top of the central atriumin the San Francisco Museum of Modern Art (68 k jpeg)

Lighting in museums and art galleries plays a key role in a visitor's ability to perceive and enjoy both the artifacts in a museum and the building in total. In order to develop a successful lighting scheme, a museum lighting designer must satisfy many conflicting design requirements. Their primary concern is effectively illuminating artwork, but they can be constrained by energy conservation standards which require light levels below 15 foot candles in some exhibit spaces. As an additional concern, they must consider the visual comfort of visitors. It is this last criteria that this report explores.

A lack of consideration for the visual comfort of visitors on a designer's part can potentially handicap an individual's ability to view displays. Dramatic variations in light levels from exhibit to exhibit, or from exterior to interior, can affect a visitor's ability to appreciate artwork because the human eye requires several minutes to adjust to large changes in light levels. Sharply contrasting light levels between a bright entry and a dark gallery can be very disturbing, and potentially even painful.

To some extent, each of these three museums uses daylight to illuminate exhibits, possibly because natural light generally creates a more positive effect on a space than electric light. This is important because the light quality can affect an individual's emotional state which in turn may affect his or her perception of the artwork. While uniform light levels throughout a space can create comfortable viewing conditions, it can potentially cause a viewer to lose interest. Some strategic variations in light levels, even though they may cause discomfort, might be an ammenity because they can make a space more visually interesting. Herein lies the challenge to the lighting designer: to achieve a delicate balance between consideration of visual comfort and creating interesting and desirable spaces.

This project presents a quick evaluation of lighting quality in these three prominent museums and compares several visitor's reported visual comfort on a typical path through some exhibit spaces. This study is limited to a brief analysis of a series of light level measurements and personal observations from a few individuals during the month of November 1995.

As discussed above, the goal of this study is to gain an understanding of the use of light in the museums through a brief evaluation--this is not a long-range, comprehensive project. However, the results from this study should still give some insight into a typical visitor's experience in each of these three buildings.

Questions for Investigation

This research project has three main concerns: visual comfort from space to space, visual comfort within a single space, and light use for architectural space-making. The findings from this investigation hopefully take a first step toward understanding each of these concerns in all three museums.

Visual comfort while moving from space to space When considering a typical circulation route through each of the three museums, how does light vary from space to space? Is the amount of variation a hindrance to the perception of the artwork or does it add to the visitor's experience? How do light levels on the horizontal plane that a visitor travels differ from those on the vertical plane of the artwork?

Visual comfort within a space All three museums use natural light in the galleries. Sometimes, especially with side lighting using natural light, glare can be a problem. Does the viewer experience glare while in any of the spaces? Does glare ever reduce a visitor's ability to engage the artwork?

Light for architectural space-making Are there noticeable changes in light levels throughout the galleries? Does light use in each space affect it positively or negatively?

OnWednesday, May 28, 2014 from 8:30 am to Noon, Scott Rosenfeld will be leading a seminar on museum lighting at The Sacramento Municipal Utility District (SMUD). There is no cost to attend, please see the link below to register. Sacramento is a 90 minutes by car from San Francisco ( if anyone is showing up early for AIC).Lighting Art and the Art of LightingNew energy efficient lighting sources are flooding the marketplace providing incredible new lighting tools along with new challenges. Museums have become an important test bed for these lighting technologies because museums demand the highest quality and employ full time professional lighting staff that maintain quality over time. LED lighting sources, in particular, present museums with a fantastic opportunity to reduce energy consumption, improve the reliability of their lighting systems, and reconsider ideas about how light can improve the visitors experience while minimizing the damaging effects of light. This talk provide an in depth discussion of museum lighting and show how these techniques can be used in a wide range of applications from retail to residential.At the core of lighting design are the five fundamental controllable properties of light (intensity, angle, distribution, color and movement). The presentation will include extensive visual examples showing how to manipulate each of these properties and then make lighting choices for exhibitions so they are better seen, understood and experienced. Special attention will be given to developing criteria so lighting products can better match users specific needs.Additional topics covered will include: a survey of LED lighting sources, how LEDs compare to legacy incandescent sources, how to access the color of light using mockups, how to access the color of light using metrics like CRI and CQS, how to utilize track lighting to its fullest potential and a review of lighting standards for light sensitive materials.The presentation will use information gleaned from the Smithsonian American Arts collaboration with the Department of Energy (DOE). The goal of the project with DOE was to match the quality of incandescent (and halogen) lighting fixtures using 100% LED technology. The museum succeeded in reducing energy costs by 70% while preserving a very similar lighting quality as the legacy incandescent lighting. The payback period, for the comparatively expensive LED lamps, was 16 months. The collaboration with DOE also identified areas where LEDs need more development. For example, unstable color and flicker in many of the MR-16 sources. The session will also include the research derived from collaborations with The Getty Conservation Institute, The Illuminating Engineering Society (IESNA), The National Institute of Standards and Technology (NIST), and various units of the Smithsonian Institution.BioScott Rosenfeld has 22 years of service as a museum professional, since 1997 as the Lighting Designer at theSmithsonian American Art Museum and Renwick Gallery. Mr. Rosenfeld is the chair of the Museum Committee for the Illuminating Engineering Society of North America and has lectured on museum lighting to many groups including PACCIN (Getty Museum with James Druzik), the Washington Conservation Guild (with Steven Weintraub), The U.S.DOE (CA & WA), The University of Florida, LightFair International (NY & NV). Scott is accredited as Lighting Certified (LC) with the NCQLP.Scott Rosenfeld is Lighting Designer at theSmithsonian American Art Museum and Renwick Gallery. Mr. Rosenfeld is the chair of IESNAs Museum Standards Committee and has lectured on museum lighting to groups including PACCIN (Getty Museum with James Druzik), the Washington Conservation Guild (with Steven Weintraub), The US D.O.E. (CA & WA), The University of Florida, AIA (DC). and LightFair (NY & NV). Scott is accredited as Lighting Certified (LC) with the NCQLP.Scott Rosenfeld is the lighting designer at theSmithsonian American Art Museum and Renwick Gallery.Scott main interest is lighting museum collections so they can be better seen, experienced and preserved. The advent of energy efficient LED lighting has led Scott to research how to measure and manipulate spectrum to enhance vision and slow the degradation of light sensitive materials. Other lighting projects include:The Hirshhorn Museum, The National Postal Museum, TheFreer and Sackler Galleries, The Walters Art Museum and The Phillips Collection.Scott is chair of the IESNA Museum and Art Gallery Committee.Scott Rosenfeld,Lighting Designer,Smithsonian American Art Museum