Una metodología de selección de iluminantes y diseño de la distribución espectral de fuentes lumínicas para la adecuada exhibición y preservación de obras de arte en museos

Abstract

In this study a new methodology of evaluation and design of light spectral composition for use in museums is presented. The hypothesis under this doctoral thesis is explained in three parts: a) it is factible to obtain a spectral reflectance curve that is representative of an artwork. b) lighting an artwork with a source which spectral emission curve matches the shape of the artwork's representative spectral reflectance curve (R.S.R.C) reduces the object's damage by lighting, that is a factor of absorbed radiation. c) the resulting visual stymulus ofthe interaction between the source's spectral emission curve (S.E.C.) and the artwork's representative spectral reflectance curve (R.S.R.C) allows for an adequate colour vision in the presentation. General objective of this study is to contribute to the fullfillment ofthe museum's mission in terms of its three aspects: presentation, conservation and efficiency. Specifical objective is to develop a methodology for illuminants selection and for spectral design of light sources composed of the following items: I) Methodology for aquisition of artwork's representative spectral reflectance curves (R.S.R.C.) II) Methodology for Illuminants selection and source spectral design for object conservation. lll) Methodology for illuminants selection and source spectral design for object presentation. A sample of artwork has been spectrally characteized, the amount and placement of spectral meassurements being enough to sufficiently describe the different sectors of the coloured surface of an artwork. Throughout a process of averaging and weighing spectral information from the different sectors of the coloured area, a representative spectral reflectance curve (R.S.R.C.) is obtained for each sample object. Using the sample objecrs representative spectral reflectance curves (R.S.R.C.) a methodology has been developed, for the design of source spectral emissions that are named MATCH and numbered after the reflectance curve from which their design derives. MATCH spectral power emissions have been obtained using the curve shape of a given R.S.R.C. that is endowed with a specific emission power. Designed source spectral power emissions and CIE illuminants have then been analyzed bycomparisson to sample objects'R.S.R.C.s which are to be lighted with them. With the aid of an ad-hoc method, a deteriorant factor has been assigned to each CIE illuminant and each designed emission (MATCH) for a given sample object. The deteriorating factor is based upon the amount of emission power that represents a specific risk of being absorbed by the object, thus producing radiation damage. Throughout this process a classification of designed emiss'ions and CIE illuminant emerges according to a the museum conservation criteria. CIE illuminants and MATCH designed emissions have also gone under an evaluation acording to the presentation aspectofthe museum mission. This results in a new classification of emissions thattakes into accountthe quality of potential colour vision, in terms of the CIE L*a*b* colour differences calculated for the colours present in an artwork sample under the lighting of a CIE illuminant or else a MATCH designed emission, compared to the same colours under the lighting ofthe CIE D65 illuminant,that is taken as reference. Results for all designed spectral emissions (MATCH 1-4) fafl within strict tolerance for CIE acceptability standards of colour differences. For both, conservation and presentation classifications, results have been experimentally validated.