Urushi Cabinet  
Urushi and Light
Urushi lacquer is very sensitive to light, especially in the range considered ultraviolet light (below 400nm) and can be damaged by overexposure. Avoid exposing lacquerware to direct sunlight or other sources of ultraviolet radiation such as halogen lamps, black-lights and sterilization chambers and avoid exposing lacquerware to strong or direct light over long periods of time.
 
Avoid Light Exposure
 
Avoid Strong or Direct Sunlight, Ultraviolet Light and Long Exposure to Light
 

Unfortunately this fact is urushi's greatest weakness and is one that any owner of lacquerware should know and understand. Overexposure to light can cause noticeable discoloration and loss of lustre and gloss of the lacquer surface. Severe overexposure (especially to that of wavelengths 365nm or less) can cause additional damage including cracking or crazing of the surface, and as a result, exfoliation of the lacquer layers. This type of damage typically will not happen in an average setting but it is clear that care should be taken to prevent such irreversible damage.

Preventing damage from over exposure to the most damaging range of ultraviolet light is not a difficult task. Simply avoiding the display and use of lacquerware in and around the strongest sources of this range of light will prevent any severe damage. Sunlight remains the strongest source of ultraviolet light will typically be encountered. Avoid using lacquerware outdoors during daylight hours and do not place or display lacquerware in front of a window or in other places where strong or direct sunlight may enter. Halogen lamps may still be encountered frequently for display lighting in stores and sometimes in the home. Although halogen lamps typically come with UV filters which effectively block a large portion of the emitted ultraviolet light, due its strong intensity and high temperatures, it is still recommended to avoid displaying lacquerware under halogen lamps. In is inadvisable to use a halogen lamp with its UV filter removed. Lacquerware should also never be sterilized in a UV based germicidal or sterilization chamber as these use strong doses of ultraviolet light in the most damaging spectrum (UV-C, 280-100nm) to kill pathogens. Other sources of ultraviolet light include various less common light sources such as high intensity discharge lamps, specialty gas discharge lamps, and certain high intensity LED lamps. Most of these particular sources of ultraviolet light would not be encountered in a normal setting, but should be avoided should the case arise.

Ultraviolet light, however, is not the only portion of the spectrum that may damage urushi. Although the level of damage is drastically reduced, light in the visible spectrum can also noticeably deteriorate a lacquer surface. Frequent, extended exposure to the visible spectrum can cause a noticeable change in color and a reduction in luster and gloss in as little as 6 years for transparent or lighter colored lacquer surfaces and 21 years for black lacquer surfaces1. In practice, this type of damage is difficult to achieve in a typical household setting, but it becomes understandable when it is suggested that urushi should not be put on constant display and be illuminated only when they are actually being viewed. Maki-e lacquerware with a heavy layer of exposed metal powder covering the entire surface, as frequently seen in kintsugi repairs on ceramics, will experience very little or no damage from this type of exposure.

Heat is also a factor in damage caused by lighting excessive heat over long periods of time also contribute to the surface deterioration in lacquerware. If lighting must be used in close proximity, only low temperature lamps such as fluorescent lamps should be used and they should be arranged to reduce the amount of heat as much as possible.

However, at times, unintended damage may still occur. If the layer is severely damaged to the extent of cracking and flaking, little can be done to restore the surface and the only measure that can be taken is to solidify the oxidized lacquer layer and prevent additional damage. However, slight damage can be reversed to some extent. Although changes in color may be permanent, a restoration treatment will typically be able to bring a slightly dulled urushi surface back to its original shine.

Nevertheless, this type of restoration effort is best avoided in its entirety and steps should be taken to prevent its need. Avoiding overexposure to light is most important, but a treatment of the lacquer surface is suggested approximately every 20 years. This treatment involves a thorough cleaning, inspection and a re-impregnation of any oxidized or damaged areas with lacquer. However, this type of treatment is not necessary to maintain the beauty of a piece of lacquerware.

With proper care, damage caused by overexposure to light is not something that will be encountered over the lifetime of a piece of lacquerware, but knowing how to avoid this damage is important to prevent it from occurring at all.

 

References:

• Ogawa, Toshio; Arai, Kazutaka; Osawa Satoshi, "Light Stability of Oriental Lacquer Films
Irradiated by a Fluorescent Lamp." Journal of Polymers and the Environment 6:1 (1998): 59-65

• Webb, Marianne, Lacquer: Technology and Conservation (Oxford and Boston, 2000)

• Araki, Tadashi; Sato, Hisayishi, "Relationships Between Exhibition Lighting and Discoloration of
Lacquered Wares." Scientific Papers on Japanese Antiques and Art Crafts 23 (August 1978): 1-24

1. JRank.org Arts, Conservation - 1. Introduction., 2. Urushi., 3. Insect and associated lacquers.,
http://arts.jrank.org/pages/9696/III-Conservation.html (21 July 2010)

 
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