Guideline 15.3

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Guideline 15.3: The lighting plan eliminates ultraviolet light

Why should the lighting plan aim to eliminate ultraviolet light from the exhibit?

In general, ultraviolet (UV) radiation is defined as wavelengths from approximately 280 to 400 nanometers (nm). Sunlight is high in UV radiation; but it is also produced by artificial lights, especially fluorescent, halogen, metal halide and mercury vapor lamps. The high energy of UV radiation is very harmful to organic objects, particularly fiber and dyes, and can damage both their physical strength and pigmentation. Because UV radiation is so destructive to organic materials and because it does not aid the human eye in seeing objects, filtering UV is easy for both exhibit designers and conservators to agree on. It is standard museum practice to eliminate it from lighting sources.

What are the options for eliminating ultraviolet light from the exhibit?

Light fixtures with a low UV output, such as light-emitting diodes (LEDs). [For more information on artificial lighting, see Guideline 15.5.]

A variety of films, filters, glass, and plastics are available that prevent UV radiation from passing through a product. In recent years, it has become possible to eliminate almost all UV radiation from any exhibition light source, and ten microwatts per lumen has become a practical goal. There are two main approaches to eliminating UV Radiation:

Using products that prevent UV Radiation from passing through window glass and exhibit case and frame glazing

• Architectural glass filtered with a laminate film
• UV-filtering glass.
• UV-absorbent varnishes. These should only be applied by an experienced contractor as the varnishes are ineffective and aesthetically undesirable when applied improperly.

Using products that block UV Radiation emitted by an artificial light source

• A variety of filters for all lamp types to reduce both ultraviolet and infrared radiation.
• Fluorescent tubes coated with a plastic that eliminates UV transmission.
• Low-voltage bulbs with an integral filter, or filtered with a treated glass.

What materials can be used to protect objects in enclosures from UV Radiation?

Exhibit objects inside enclosures can be protected from UV radiation by:

• Constructing the enclosure with UV-filtered glazing to block UV radiation from passing into the enclosure
• Glazing the frame package with UV-filtering material to block UV radiation from passing into the enclosure
• Installing a layer of UV-filtering material between the lights in a case’s lighting chamber and the objects to block UV radiation coming from light sources within the case.

[For further discussion, see Case Standards *.]

How can objects on open display be protected from UV radiation?

For vulnerable objects on open display, a large-scale approach to mitigating the hazard of UV radiation must be used:

• If windows cannot be blocked, UV-filtering films or glazing should be used to prevent UV radiation from passing through.
• UV filters for all artificial light sources should be used.
• Films produced for theatrical productions and those used to control UV, visible, and IR radiation passing through architectural glass can be used to lower the amount of radiation in some exhibit situations. These films are placed between the light source and the viewing area.

What are the different options for filtering UV Radiation?

Use the following three charts to guide your selection of UV filtering products. The charts provide filtering options for:

1. fluorescent lamps
2. tungsten-halogen lamps
3. architectural glass