druzik, j. research on museum lighting. gci. 2007

8/3/2019 Druzik, J. Research on Museum Lighting. GCI. 2007

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Conservat ion

The Getty Conservation Institute


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The GettyConservationInstituteNewsletter

Volume 22, Number 3, 2007

The J. Paul Getty Trust

James Wood President and Chie Executive Ofcer


Timothy P. Whalen Director

Jeanne Marie Teutonico Associate Director, Programs

Kathleen Gaines Assistant Director, AdministrationJemima Rellie Assistant Director, Communications and Inormation Resources

Giacomo Chiari Chie ScientistSusan MacDonald Head o Field Projects

Conservation, The Getty Conservation Institute Newsletter

Jerey Levin Editor

Angela Escobar Assistant Editor

Joe Molloy Graphic Designer

Color West Lithography Inc. Lithography

The Getty Conservation Institute (GCI) works internationally to advance

the feld o conservation through scientifc research, feld projects,

education and training, and the dissemination o inormation in

various media. In its programs, the GCI ocuses on the creation and

delivery o knowledge that will beneft the proessionals and

organizations responsible or the conservation o the visual arts.

The GCI is a program o the J. Paul Getty Trust, an international cultural

and philanthropic institution that ocuses on the visual arts in all their

dimensions, recognizing their capacity to inspire and strengthen

humanistic values. The Getty serves both the general public and a wide

range o proessional communities in Los Angeles and throughout the

world. Through the work o the our Getty programsthe Museum,Research Institute, Conservation Institute, and Foundation

the Getty aims to urther knowledge and nurture critical seeing through

the growth and presentation o its collections and by advancing

the understanding and preservation o the worlds artistic heritage.

The Getty pursues this mission with the conviction that cultural

awareness, creativity, and aesthetic enjoyment are essential to a vital

and civil society.

Conservation, The Getty Conservation Institute Newsletter,

is distributed ree o charge three times per year, to proessionals

in conservation and related felds and to members o the public

concerned about conservation. Back issues o the newsletter,

as well as additional inormation regarding the activities o the GCI,

can be ound in the Conservation section o the Gettys Web site.

www.getty.edu


1200 Getty Center Drive, Suite 700

Los Angeles, CA 90049-1684 USA

Tel 310 440 7325Fax 310 440 7702

2007 J. Paul Getty Trust

Front cover:Testing an inkjet print to determine itscoating. Inkjet papers oten have special coatings thathold the colorants at the surace, resulting in a higherquality image. A spot test with a minute droplet o water,perormed under a microscope, may help establish i thecoating is a porous or polymer type. Porous coatingsabsorb water, while polymer coatings swell due to theirhigh gelatin or polyvinylalcohol content. This distinctionis useul in evaluating exhibition and storage conditions

or these prints. Photo:Martin Jrgens.


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I one wishes to improve existing practices or to examine this

mediumwhich both communicates and destroysin any detail,

the complexity almost immediately rises up as a barrier to progress.

Investigating Museum Lighting

Since 2002 the gci has been investigating museum lighting in some

depth. Initially the research questions were about reducing the total

energy fux to objects on display beyond what we have been able to

achieve thus ar by lowering light levels, reducing exposure time,

and removing ultraviolet light. But one cannot reduce energy and

preserve the color appearance o valuable artiacts without a

undamental understanding o color science and optical physics.

We had to consider visual perormance and aesthetic satisaction,

particularly with regard to lighting systems that diverge rom well-

used and understood lighting techniques. It was also necessary toexplore materials damage anew. Our knowledge o how most

pigments, dyes, and substrates react to blackbody radiators such

as sunlight and incandescent light sources, especially with unknown

historical light or pollution exposures, is sadly incomplete. The

proession o conservation has managed to create a sufficient

number o heuristic procedures to approximately manage the

problem. And as a proession, we have recently seen the creation o

new tools (and the improvement o old ones) that greatly enhance

the early detection o light-sensitive colorants. But this body o

knowledge is based on three spectra proles: daylight, low-color-

temperature incandescent, and low-to-high correlated color

temperature fuorescent illuminants. To diverge rom these three

classes is to enter poorly explored territory in materials damage,

visual perormance, and aesthetics. Even the tried-and-true compu-

tational tools may not serve with the same relevance as they once did.

Thereore, since 2002 the gcis research has had to amalgamate all

these actors into a museum lighting project that had originally (and

naively) been thought to simply involve reducing the fux o energy

to suraces.

20 Conservation, The GCI Newsletter| Volume 22 , Number 3 2007| News in Conservation

MMuseum lighting is the most complex environmentalparameter surrounding museum collections. Experience tells us thatit ranks high in its potential to damage cultural artiacts throughading and other visible changes. But lighting can also introduce,

into otherwise stable microenvironments, energy that may altermaterials in less visible ways. O course, museums cannot simply

dispense with lighting. You can restrict the diffusion o oxygen into

microenvironments, control the fow o water molecules, maintain

temperatures at rock-solid levels, and set implacable limits or other

actorsbut excluding photons is simply inconsistent with exhibit-

ing works o art and thereore with many o the educational unc-

tions o museums. Thus, we have come to accept a range o

compromises that manage an acceptably slow rate o damage rom

light exposure. However, these risk management procedures would

not make museum lighting any more remarkable than other environ-mental risk actors i human sensory and cognitive apparatus were

not part o the equation.

Unlike pollution, incorrect relative humidity and temperature,

shock and vibration, and museum pests, lighting is critical or

communicating inormation about an objecte.g., its color appear-

ance or patterns o contrastor conjuring up visitors associations

with an objects historical milieu or aesthetic context. Lighting oten

complements the architectural environment into which objects have

been placed and evokes a host o purely serendipitous personal

responses in visitors. Complicating the myriad responses to design

and communication elements are each visitors perceptual con-

straints. Older visitors need more light to see the same level o detail

as younger visitors. Their sensitivity to tonal contrast is reduced,

their color perception is altered, and their acuity is requently

reduced; complex visual tasks take more time. Overlay these realities

with curatorial decisions on conservation lighting practices

some o which affect the visitors experience even urtherand it

becomes clear why lighting is so complex. For a variety o reasons,

much o this complexity is simply not addressed by museums.

Research

onMuseum

Lighting

a project update

By James Druzik


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Conservation, The GCI Newsletter| Volume 22 , Number 3 2007| News in Conservation 21

Another consideration is the current change in the wind

with regard to energy policy that extends well beyond museum walls.

Energy policy reorm in the United States and other developed

countries is merging with new technology to produce changes that

will challenge museums. Incandescent sources are inefficientwhatcan be done with ty watts is attainable with compact fuorescent

lighting (cfl) at twenty. Light emitting diodes (leds) and other solid-

state sources can do even better, and leds have almost no attendant

waste management issues, unlike cfls (in spite o their reduced

mercury content). leds also hold out the hope or exceptionally long

operational lietimes. Because o recent experience in gallery

remodeling at the J. Paul Getty Museum in Los Angeles, the Getty

is especially aware o laws in Caliornia that now limit the amount

o light used per unit o area in display situations, as compared with

what was permissible in the mid-1990s. There is every reason toexpect that policy extrinsic to museums and conservation practices

will orce the conservation proession to adjust. Thus, the tool sets

and mind sets developed since 2002 as part o the Museum Lighting

project will serve other purposes as well.

Work Conducted

The gci and its research collaborators have developed methods or

satisactorily illuminating collections o artworks such as old master

drawingswith clearly limited ranges o colorants and appearance

propertieswith lighting that reduces the intensities or some o

the requencies in the visible range (in contrast to the unltered

quartz-halogen lamps oten used in exhibitions). The principal

collaborator or this research, Carl Dirk at the University o Texas

at El Paso (utep), has developed multicoated glass lters that

provide excellent color rendering o old master drawings while

reducing irradiation. Various newly written mathematical models

or calculating color appearance, color rendering o light sources,

and spectral proles have been combined with industrial engineer-

ing design sotware to produce testable lters that offer the desired

discontinuous spectra.

kGCI senior scientist James Druzik lookingat a copy o an old master drawing hungin a specially designed display case.The light in the case, which passesthrough a flter designed by researchersat the University o Texas at El Paso(UTEP), projects less than hal o thetotal energy o an unfltered quartz-halogen light o equal illuminance.Human visual assessments were used totest the fltered light or visual satisac-tion and color-rendering capacity.Photo:Emile Askey.


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Over the last year, both at utep and at the gci, work has

progressed on two main rontsvalidation o the visual appearance

model predictions and testing o the effects o these lters on light-

induced accelerated aging. The rst aspect o this work nears

completion or three o the experimental lters developed by utep.

These lters have been assessed or visual satisaction and subjective

color rendering by more than a hundred individuals. Fity o these

assessors have been museum conservators, curators, educators, and

library and acilities support personnel, and thirty were selected

rom the Getty Museum docent program. Capturing the younger

demographics, uteps program used university students almost

exclusively. This selection ensured a ull range o proessions

associated with museums, as well as age groups o widely varying

museum experience, visitation habits, and expectations.

A big challenge was how to carry out human visual

assessment o lighting. Focus groups are popular, but they tend to

suppress weak individual responses in avor o deriving consensus;

they can bias some o the members, and thus, members cannotstatistically be treated evenly. It is ar better to poll assessors singly

and treat responses as independent statistical units. Internal checks

and balances can be built into the assessment orm to ensure that

the data derived are air or what is being evaluated, and collecting

unormatted comments about the assessment process helps to

determine i a line o questioning is garnering weakened or useless

22 Conservation, The GCI Newsletter| Volume 22 , Number 3 2007| News in Conservation

data. Thus we have employed a combination o psychophysical

testing (or color-anomalous vision and intensity-matching experi-

ments), color discrimination o light source chromaticity (Is light

source A redder than light source B?), and visual satisaction

assessment (On a scale o one through seven, how would you

rank your satisaction o light source A?). The American Society

or Testing and Materials (astm) has a standard or color assess-

ments that can be used to inorm museum lighting assessment

procedures, but there is no standard or solely judging museum ne-

art aesthetics.

The human visual system is tricky to test. First, the level o

brightness adaptation must be controlled. It is easy to understand

that we need to adapt to darker environments when coming in out

o bright sunlight, but this phenomenon also holds true when we

move rom high light levels or paintings to low light levels or dark

or low-contrast artworks on paper. We are also seldom conscious o

how chromatic adaptation modies our perceptions. The human

visual system successully and rapidly white-balances many lightsourcesi.e., it corrects or excessive color casts such as blue, red,

or greenin such a way that we hardly notice their signicant

chromatic differences. In other words, this chromatic adaptation

makes amiliar and common objects appear natural through an

extremely rapid, and usually unconscious, refexive action. To

compare two light sources airly, we need to allow the viewing

n

The author preparing to measure thecolor change o a sample aterexposure to light fltered through aUTEP-designed flter. Highly light-sensitive colorants may not beappreciably helped by the exclusion oUV wavelengths rom illumination.Photo:Emile Askey.


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Conservation, The GCI Newsletter| Volume 22 , Number 3 2007| News in Conservation 23

periods o exposure. We have known since the early 1950s (rom

independent researchers such as McLaren, Morton, and Taylor)

that highly light-sensitive colorants may not be appreciably helped

by the exclusion ouv wavelengths rom illumination. Compounds

like rhodamine, methyl violet, and some color toners continue to be

added to artists paints and are so light sensitive that probably

nothing, save darkness, will keep them rom extinction.

Even lters like the ones we have designed and abricated may

offer little or no help or some materials. Thus we need to proceed

slowly and deliberately. The current set o lters consisted o

prototypes, with the main aim being to reduce total radiant energy,

preserve luminance, and maintain adequate color rendering. In this

rst stage o lter development, the principal challenges were the

creation and implementation o new theory applicable to the

problem, the creation o computational methods to address the

problem, and the identication o adequate manuacturing methods.

The research conducted as part o the utep-gci collaboration has

demonstrated that color and optical theory can be developed tocontrol light in the key areas o color rendering, radiance, and

luminance to yield spectral proles optimal to preserving works o

art. This research has demonstrated urther that manuacturing

techniques and materials can be identied to make long-lie lters.

In less than ve years, utep and gci researchers have assembled a

complete set o toolsdesign concepts, sotware, and abrication

methodsthat can help redene how uture museum lighting

research proceeds. Once these techniques are published in the

proessional literature, other researchers in the eld o museum

lighting will have an enhanced ability to effectively evaluate theirwork, and this ability should assist in the continued evolution o

improved techniques or illuminating works o art.

Our biggest challenge or the last and remaining year o this

project is to be absolutely precise on the degree o benet such strat-

egies as these afford or the protection o light-sensitive works o art.

Light aging must be pushed to higher degrees o precision than are

requently ound, since valuable, oten irreplaceable artiacts are at

stake. Much work remains to be done to optimize color rendering,

lower overall energy exposure, and ensure colorant permanence.

We hope to be able to report in a uture article that the lters we aredesigning and testing are ready or installation.

James Druzik is a senior scientist with the GCI. He oversees the Institutes Museum

Lighting project.

environment to permit this adaptation as i nothing about the light

sources differed. In what we call the threshold test, assessors are

given a alse acuity task and then, once they are removed rom the

test environment, they are asked what they remember about light

intensity, evenness o illumination, and chromaticityaspects o

the test they were not previously told to pay attention to. When we

combine this test with the other evaluation criteria, we believe we

are able to determine how acceptable the ltered light sources are,

compared to conventional lighting, or a cross section o museum

proessionals and visitors (given the limitations o our sampling);

assessors are not told which lighting setup is which, and their order

is alternated. At utep, test subjects uniormly could not distinguish

between the utep-designed ltered and unltered lighting. This

nding was true, regardless o age, sex, or background.

Long-term and accelerated testing o the utep-designed

lters suggests practical lietimes or the lters that exceed at least

six years o typical use, with an upper temporal lietime limit yet to

be determined. The manuacturing techniques and materials appearto be robust.

During the last year, we began measuring the effects o two o

these lters on several sets o pigmentscompared to no ltration

or compared to ltration that removed only ultraviolet wavelengths.

These tests all into the realm o accelerated light aging, but they are

perormed at light levels low enough to require rather lengthy

kA view o an installation at the exhibitionFade: the Dark Side of Light at theCaliornia Science Center (CSC) inLos Angeles. This exhibition, coproducedby the GCI and the CSC, explores thedestructive eects o light exposureon objects and the work o the MuseumLighting Project to reduce these eectswhile minimally aecting visualperception. Photo:Courtesy theCaliornia Science Center.

druzik, j. research on museum lighting. gci. 2007

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