: On Tue, 3 Jan 1995, Alex Barker wrote: : > Does anyone have experience with the use-life (and general usefulness) of : > fluorescent light UV filters? How long do they remain effective? : > : > Alex Barker : > It depends on the materials in the filter. Most of the polyester and acrylic UV filters now produced should be stable for a decade or more, but some tests we ran on extruded plastic (acrylic?) sleeves revealed that over time the heat from the bulb will degrade the plastic, causing minute crazing that allows light to pass through relatively unfiltered. This crazing can be easily seen if the sleeve is gently squeezed. (tech talk: the aged sleeves exhibited transmission curves that were centered at about the same frequency (400nm) as the new samples, but the aged curves were considerably sloped, indicating both an increase in effectiveness caused by plastic yellowing, and a decrease caused by film degradation (crazing), the net effect being a decrease in UV filtration) Moral: if you are going to use extruded sleeves, replace them when they look darker at the ends, otherwise, purchase or borrow a UV meter and check every five years or so. John Burke, The Oakland Museum