MUSEUM LIGHTING / EXPERT OPINION MUSEUM LIGHTING / OPINION
Kit Cuttle runs through the different lighting settings for museum objects related to their visible and material attributes.
THE ART OF LIGHTING
Figure 1 (far left): An uncontrolled ‘flow of light’ from a line of windows generates a powerful shading patterns as it interacts with ‘The Kiss’ at the Rodin Museum, Paris, France.
Figure 2 (left): This modern interpretation of the classic European picture gallery employs diffusion to achieve a controlled daylight distribution at the Sammlung Essel, Klosterneuberg, Austria.
Lighting designers should recognise that a museum may be so much more than just a building in which exhibits are presented. It can provide a setting that forms an in- tegral part of a visitor’s visual experience. However, the ways in which this may be achieved are strongly influenced by the sus- ceptibility to light exposure of the materials on display. The International Commission on Illumina- tion specifies four categories of mate- rial responsiveness to light exposure (CIE 157:2004, Control of Damage to Museum Object by Optical Radiation), and in Table 1 these are indicated ranging from R0 (non- responsive) to R3 (highly responsive). The figure also shows these R categories related to four categories of lighting control, rang-
ing from L0 (uncontrolled daylight) to L3 (minimal exposure). The rule is that the R rating of the material should not exceed the L rating of the lighting, which take account of the range of lighting parameters that contribute to damage exposure. A display of R0 materials gives the designer the most degrees of freedom for revealing the visible attributes of displayed objects in their settings. Figure 1 shows a superb interaction of light with an object that is, at least from the conservation point of view, totally non-responsive. ‘The Kiss’ is dis- played in the Rodin Museum, Paris, and at the time of my visit, the flow of light in this setting brought this classic sculpture into strikingly beautiful relief. Obviously, the illumination is daylight, but the building in
Table 1: Summary of the principal control factors relating to the ambient and display illumination in museum galleries.
which Rodin’s works are displayed was not designed to be a museum. It was, in fact, a mansion owned by an aristocrat, and the daylight flows into this space through a line of arched windows that provide views onto the surrounding gardens. It is a lovely set- ting and, depending on the vagaries of the weather, a visitor may experience lighting that reveals this sculpture quite beautifully. This is a fine example of an excellent visual experience in a R0/L0 situation. If some of the materials on display are slightly responsive to light exposure, the R1 category applies and so the lighting must be L1 or higher. Figure 2 shows a daylit picture gallery suitable for oil paintings (but not watercolours) in which the architect, Heinz Tesar, has developed a modern interpre- tation of the classic European gallery, moulding the picture-hanging walls into the characteristic curved ceiling vault. The lan- tern skylight achieves sunlight and daylight control through diffusion that, in combina- tion with the high reflectance wall surfaces, produces a soft, shadow-free illumination giving an even wash of light over the walls. Museums typically aim for an illuminance of 200 lux for R1/L1 situations of this sort, which may be achieved entirely by daylight, as in this case, or by electric lighting, or a combination of the two. Where the propor- tion of daylight is high, it is not practical to treat the 200 lux value as a maximum, but rather it should be treated as an average value that may be exceeded some of the time, and as the daylight level fades, the display illuminance will become increasingly
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