LIGHTING AND ENVIRONMENTAL CONTROL IN THE SACRISTY OF THE MONASTERY OF OUR LADY OF GUADALUPE IN CACERES

The sacristy of the monastery is a baroque architectural complex of great historic and artistic value, containing an important series of oil paintings by Zurbanin executed between 1636 and 1638. From the point of view of conservation and exhibftion of art objects, at least three factors have been taken into account when designing the new installation in the sacristy. First, there is the placing of the Zurbanin paintings in their rightful context; second, the relationship between these paintings and the extensive and detailed fresco decoration of the vaults and surfaces, attributed to Manuel Ruiz; and last, the double function both liturgical and as a museum of the space. In the fall of 1988, as part of a programme to address the conservation and restoration of the building, a study was made of the environmental conditions and lighting, both natural and artificial. The windows face south and between each pair there is an oil painting by Zurbaran (three in all). Two problems were identified: excessive illumination of the paintings on the north wall in winter and excessive contrast between the canvases and the contiguous windows. The best solution was to position screens made of linen to limit both the incoming light and the luminosity of the glass surface, thus greatly improving viewing conditions for the paintings situated next to the windows. The light levels inside the sacristy were first calculated. The artificial lighting is mounted on the cornice and consists of two different types of system for fluorescent lamps. The first is indirect: 10 light fittings with compact fluorescent lamps and a total power of 360W. The second is both direct and indirect, comprising a line of (high frequency) fluorescent lamps, with a total power of 720W. The latter is specially designed to give asymmetric light distribution. The paintings on the north wall are illuminated from the bottom of the windows on the opposite side, using linear halogen lamps in fittings which produce an asymmetric light distribution. The frontal lighting, above the line of sight, guarantees the absence of glare. The paintings on the south side are illuminated from the cornice on the opposite side, at a sufficient angle to eliminate glare in the frontal position. The average level of illuminance on the canvases is 70 lux, adding both lighting systems together. In order to obtain significant data, various observation have been made: