Museum Lighting Protocols (1998-31)

22 September 2008 by NCPTT (about the author)

1998-31

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Museum conservators and the like are well acquainted with the fact that some types of museum exhibits are susceptible to damage caused by exposure to light. Currently, such unwanted effects are often mitigated by avoiding non-visible light (UV and IR), limiting light level and restricting exposure duration. This approach can only go so far.

The work in the Museum Lighting Protocol Project seeks to extend recommendations to include the potential of incident light in the visible spectrum to stimulate the sense of brightness (illuminance) and balance that against its potential to cause damage (irradiance). Instead of providing light with a smooth curve throughout the visual spectrum like current incandescent filament light sources, the authors propose a lighting methodology using illumination from only three spectral bands. This three-band source would have enough visual satisfaction as the incandescent sources while providing significantly less irradiance.

Documentation on the theory, artwork and tests are all included in the report. There were various chromatic and achromatic works studied in differing color temperatures, both in the incandescent source and the experimental three-band source. The overall result is that for the same illumination and visual satisfaction, the three-band source had very significant lowering of the irradiance incident on the exhibited works. Subjects were questioned about any apparent differences they noticed, generally reporting only slight differences. The nature and import of the differences is discussed and the authors conclude that a practical light source for museums that utilized similar three-band light sources could be developed with equal visual satisfaction at equal illuminances. This would expose the exhibits to significantly less irradiance and thus reduce the rate of degradation of the objects on display.