1 1. INTRODUCTION

Among the many agents that damage museum objects, light is regarded as one of the most pervasive and harmful. The UV region is noteworthy because many materials absorb light within this region. The light-absorbing chromophores they contain often enter into or stimulate undesirable reactions such as photochemical oxidations and reductions and the cleavage and formation of bonds (Reinert et al. 1994). All organic objects are at risk when exposed to light, including objects made from textiles, paper, wood, parchment, leather, and feathers. Because the action of light is cumulative, reducing the illuminance and exposure time and screening out the most harmful UV rays may slow light damage to objects. For storage areas, Garry Thomson (1986) suggests that a good UV filter should transmit less than 1% of the incident radiation between 320 and 380 nm. Fabric covers are sometimes used to protect objects from UV, visible light, and dust in conservation laboratories and museums. Black textile covers are used in the textile conservation laboratory at the Metropolitan Museum of Art. At the Isabella Stewart Gardner Museum in Boston, decorative textiles cover many glass display cases, and sheer fabrics on the windows act as light screens. Fabric covers on display cases are moved aside by visitors when they want to view the objects. In historic homes, textile covers protect upholstered furniture when visitors are absent. Window blinds and draperies are used to control the illuminance because window glass filters some but not all UV radiation between 300 and 400 nm (Thomson 1986).

Although textile covers are routinely used for protection against damage by light, how well various fabrics screen UV radiation has not been reported in the conservation literature. The principal research objective of the present study was to determine how effectively various textiles and tissues typical of those used for this purpose in a conservation laboratory or museum block the transmission of UV radiation. A second objective was to measure the fiber, yarn, and fabric characteristics that contribute to the blocking of UV radiation and to determine the relative importance of each in that regard.