Sun fading, has been and will always be a problem with Navajo Weavings. Here is an article written by my mentor Bob Morgan and old friend Jenne Brako. This worksheet was written for the Mountain Plains Museums Association August 1986. This has become the standard for Navajo Textile Conservation and long term care.
Light is one of the great enemies of Navajo textiles. Although light enhances the visual beauty of the weaving, both artificial and natural light contains invisible ultra violet rays. Even visible light is damaging.
As with all organic artifacts, keep Navajo textiles away from direct sunlight. The recommended visible light intensity level for textiles is five foot candles (fifty lux).
Exposure to ultraviolet (UV) light causes weakening of the wool fibers, yellowing and permanent color change. Color shifts occurs especially with synthetic dyes, which tend to be combinations of several component colors. For instance, black may be composed of blue, red, yellow and brown dyes, with each dye fading at a different rate. Pre-1900 aniline blacks tend to fade to purple with the loss of one or more components. Greens show similar phenomenon, although the shift is towards a yellow hue. Reds tend to show a fading in value (lightening) rather than a color shift.
Many of the vegetal dyes employed by Navajo weavers are extremely fugitive and fade quickly when exposed to UV light. This phenomenon is especially problematic in the Rocky Mountain-High Plains region because of the elevated UV levels a higher altitudes. Light can also bleach natural fleece colors.
Ultraviolet levels should be filtered, using UV filtering material on windows and display cases (Rohm and Hass UF-3 plexiglas: 3-M Solar screen). Special filtering sleeves should be used to cover florescent lights, which emit high levels of UV radiation.
Screening out UV radiation will diminish the harmful effects of light, but will not prevent visible light levels from damaging the weaving. The damaging effects of light are directly proportional to the amount of light times exposure. Limit display to three or four months per year. If the amount of light cannot be modulated, decreasing exposure time alone will decrease the deleterious effect of light.
Just to clarify and on a personal note. I have a client in the Los Angeles area who was a huge collector of Indian pottery. With one earthquake and insurance money he became a collector of Navajo Indian textiles. Navajo weavings are very durable, this example is an extreme example of sun fading and not rotating and or flipping of the weaving.
When this worksheet was written, it was for conservation and museums to reduce longterm damage too weavings on display at museums. Navajo weavings are extremely durable. This should not be a deterrent to anyone interested in collecting. A little common sense like flipping the weaving over time to time and avoiding having the weaving in direct sunlight will keep your weaving as an heirloom for generations to come with little or no long term effects.
Below is an extreme example of sun fading. As you see the weaving was never flipped over and just one side was exposed to direct sunlight, day in and day out. The other side looks almost as if came right off the loom.
Unfortunately, sun fading is permanent. Although I have seen weavings that are airbrushed or hand painted with a dye than one might cover it with a soil protector to cover the dyed wool. Over time if and when the fabric protector wears off or breaks down then the dyed areas will loose the airbrushed /hand painted dye and the weaving will go back to faded.
If you are starting to collect or an old pro. When going out to purchase a weaving and it is a very shinny old rug, I myself would carry a old white cotton hanky or white sock and give the colors a little rub. If color rubs off onto the hanky or sock easily I would pass on the weaving because most likely it is sun faded and painted to look original and will return to the faded look eventually.