An early warning system for light damage in museums and exhibitionsM. Baccia, C. Cuccia, S. Gerlachb, H. Roemichb, A.-L. Dupontc, B. Lavedrinec and G. MartindaIstituto di Fisica Applicata "Nello Carrara"-(IFAC), Via Panciatichi, 64, I - 50127 Firenze bFraunhofer- Institut fr Silicatforschung, Bronnbach Branch, D 97877 WertheimcCNRS / CRCDG, 36, rue Geoffroy-Saint-Hilaire, F - 75005 ParisdVictoria & Albert Museum, South Kensington, SW7 2RL London

Interaction between light and the art objectTo be appreciated by the observer, the object needs to be illuminated, even if light can cause irreversible damage to the coloursA compromise has to be reached so as to allow a satisfactory reading of the painting while keeping the lighting at sufficiently low levels

Lighting is not the only cause of colour fading. The presence of pollutants and unsuitable temperature and humidity conditions can amplify and accelerate photo-alteration processes

THE EQUIVALENT LIGHT DOSE (ELD)Co-operative effects cannot be correctly evaluated by a separate measurement of each environmental parameterIn order to give a semi-quantitative indication of the amount of the cumulative damage we have introduced the concept of ELD

DEFINITION OF EQUIVALENT LIGHT DOSEThe ELD can be defined as the light-dose which is capable of producing, in a given material in an uncontrolled environment, the same spectral variation as that measured in the same material exposed under well-defined and controlled environmental conditions

Accepted annual luminous exposure limits from published data (Ttrault,2003)

CategoryExamplesofartefactsAfter 100 years, a just noticeable fading will result from a maximum luminous exposure ofHigh sensitivityISO 1,,3Graphic documents, albumen prints, colour photographs, parchment, leather, textiles, tapestry, natural history specimens10 000 lux h per yearModerate sensitivityISO 4,5,6Oil paintings, tempera, wood, polychrome sculptures, bone, ivory100 000 lux h per yearLow sensitivityISO 7,8, aboveStone, metals, ceramics, B/W photographs3 000 000 lux h per year

The global microenvironment can be much more dangerous to paintings than light alone

After 9 months of natural exposure in different museums, some tempera sensors, which were prepared for this purpose (ERA project, Contract N. EV5V CT 94 0548), showed alterations even in a controlled environment: in some cases, this exposure corresponded to more than 50 years of exposure to lighting of 200 lux.

Installation of the IFAC-CNR prototype inside the Geographic Maps roomat the Uffizi GalleryAutomatic recording of the dosimeter colourELD is evaluated on the basis of a previous calibration, performed by means of an accelerated ageing testA photodiode measures the actual light

A test of equivalent-light dosimetry over 300 days Uffizi Gallery IFAC-CNR laboratory Travel to and exhibition at Valladolid, Spain

A simple measurement of the light dose could be not sufficient to assess a possible riskWe have verified that in natural conditions the fading is always greater than the expected one on the basis of the light dose receivedTherefore

Need for a device, which, in some way, can integrate the effect of the different environmental factorsA light dosimeter for monitoring cultural heritage: development, testing and transfer to marketLiDo ProjectEC-contract EVK4-CT2000-00016

SUPP-CZ

data-logger recordingVIS light, UV, T, RHLCU

BWS1 - Evaluation of effects of the exposure in terms of the colour change (DE*) - Investigation on the relationship: DE*Luminous Exposure (= It) LCS

Maest , Giotto (c.1310)-Uffizi Gallery-Florence The basic idea:

The aim of the project: development and testing of light dosimeters and their transfer to the marketSelection of dyes/matrices/substrates Laboratory experiments Field applicationStandardisation of the preparation method SUPP-CZExposure of light dosimeter in the V&A London next to sensitive carpet

To obtain a colour variation of DE 10-12the exposure needed is 12 kluxh for LCU 60 kluxh for LCS 250 kluxh for BWS1

A comparative test: LightCheckU, LightChekS and BWS1 Calibrations curves Artificial light-ageing in light-chamber - (500 lux quartz halogen lamp at T=23 C, 50 %RH)

Different degrees of light-sensitivity are found light-sensitivity

BWS - LCS - LCU

LCSLCULCS and LCU work in a fashion analogous to that of a pH indicator

LIGHT DOSIMETERS LTD32 CAMDEN LOCK PLACE, LONDON NW1 8AL, U. K.TEL + 44 207 267 7555, FAX + 44 207 267 1555UK VAT REG NO. 828 5021 35e-mail: david@outlookres.co.uk

All North American enquiries should be to www.keepsafe.caAll French speaking enquiries should be to www.atlantis-france.comAll German speaking enquiries should be to www.cwaller.deAll other enquiries should be to david@outlookres.co.ukLCU and LCS started being sold in June 2004. First clients include the National Library of Czech Republic; the National Library of Ireland; the Tate Museum, London; the Getty Museum, California; the Smithsonian, Washington D.C. ; the Victoria and Albert Museum, London; the National Museum of Sweden; the National Trust, Britain

ACKNOWLEDGEMENTSThis work was supported by the EC Project LiDo: A light dosimeter for monitoring cultural heritage: development, testing and transfer to market (EVK4-CT-2000-00016), under the Fifth Framework Program. Thanks are expressed to Dr. Anna Maria Petrioli and Dr. Antonio Natali (Soprintendenza Polo Museale fiorentino), who allowed the authors to place the dosimeters in the Uffizi Gallery.