As an objects conservator I would explain that while UV is the most harmful spectrum of light blocking it doesn't mitigate from the damage from the rest of the effects of light on museum collections. Light damage is cumulative and not reversible. Meaning that both the intensity of light and the duration of exposure add up to damage and deterioration to light sensitive collections. Light also provides energy to photochemical reactions on materials. It fades paint pigments, dyes in textiles and inks, and bleaches wood. Take silk as an example. If you put a silk flag in sunlight within weeks the red color fades and within months the silk can become brittle and "shatter". The same thing happens to silk flags and dresses in museum collections from light exposure. So, in controlling light, while the UV film helps, elimination light from windows in exhibits is better. Florescent fixtures can blast collections, so if you can use other light fixtures with far lower UV (such as LED lights) instead, that's better. Otherwise, put UV film over your flourescent tubes. The UV films will age and become ineffective and have to be replaced. The only sure way to know is to measure the UV levels directly over the objects using a light meter. There are many strategies in controlling light in exhibits that provides adequate protection while still making the exhibits visible. You also need to identify the most sensitive objects/materials and establish a rotation schedule to lessen the duration of time on exhibit. Examples include textiles (especially silk), photography (especially color), books and works on paper, and paintings that contain light sensitive pigments and paints. You also need a policy to prevent staff and volunteers to change light levels in the exhibits. This is why venetian blinds may not be the best solution. Each museum and exhibit space is different so you should get a conservator or museum lighting expert who has experience with preventive conservation in lighting issues in to do an onsite assessment and make recommendations. It would be a perfect small IMLS collections stewardship grant.

Cheers!

Dave

David Harvey

Principal Conservator & Museum Consultant

Los Angeles, CA. USA