Deterioration of UV filters

Barbara Appelbaum <aandh<-a t->village< . >ios< . >com> writes

>On the question of the deterioration of the UV-filtering power of various
>UV shields, does anyone have data--either from laboratory measurements or
>from measurements in use--related to UV transmittance?  Since many of
>the plastic carrier materials yellow with age and therefore absorb more at
>the blue end of the spectrum, I understood that UV transmittance can
>increase rather than decrease.

I suspected this to be true as well.  I called and wrote to all the
manufacturers in the mid 1980s for test information.  Like the
article I published in the AIC Newsletter a few years ago on spray
fixatives, getting information from the manufacturers was near
impossible.  The verbal response was that after 7 to 11 years,
effective UV absorption (blocking) is substantially diminished.  Bob
Futernick used the data I collected for a report for the Fine Arts
Museums on UV blocking systems.  He did some experiments on
individual UV plexi glass types.  You might call him and see if he
still has the data.

Niccolo Caldararo
Conservation Art Service

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                  Conservation DistList Instance 10:73
                Distributed: Tuesday, February 18, 1997
                       Message Id: cdl-10-73-004
                                  ***