4 CONCLUSIONS

THIS RESEARCH SUPPORTED EARLIER WORK3 which showed that some natural dyes were afforded no protection by the essentially colorless filters, i.e., those with a light yellow tint. Controlling level of illumination to the level recommended for textiles (50 lux) is more beneficial than the use of essentially colorless UV filters in protecting some, if not most, natural dyes from fading. UV filters of polyester film with a reflective silver coating are the recommended filtering material when amber-tinted filters distort color objectionably but when greater protection of artifacts is desired than that afforded by filters with very light yellow tints.

The only filters that were significantly altered by 600 AFUs of light exposure were the amber-tinted flexible filters that lightened perceptibly and whose spectral curves were altered. Neither the rigid acrylic nor the other flexible filters were perceptibly altered by 600 AFUs of xenon light exposure. The amber filters would require more careful monitoring and a shorter replacement schedule than the other types of filters.

ACKNOWLEDGEMENTS

THE AUTHOR THANKS David Clark and Lisa Thorson, research assistants, for their dedicated assistance during the lengthy light exposure and data collection process. SolarScreen and Rohm and Haas provided generous samples of ultraviolet filtering materials. Galvin Glass Inc. (Lincoln, Nebr.) cut all acrylic sheets to specimen size for light exposure. The Agricultural Research Division, University of Nebraska, partially supported this research, which is published as Journal Series Number 8704.