For both artists and art collectors, the fading of an oil painting can be a great concern. Museums and galleries have climate controlled windowless rooms and trained curators on staff to care for and preserve their collections. Even without the help of professionals, there are some steps you can take to prevent an oil painting from fading. However, it should be noted that depending on the materials used to create a painting, some are still prone to fading with or without proper care.
Direct Exposure to Sunlight
The biggest cause of fading in oil paintings is sunlight. The same UV rays that can damage human skin can cause the colors in an oil painting to fade over time. As you might expect, the most sunlight damage occurs to paintings kept outdoors in direct, unfiltered sunlight. Murals or paintings meant to decorate the side of a building may become faded by outdoor sunlight. They also run the risk of additional damage from being outside in the elements. Also at risk are paintings placed near windows that are routinely kept opened. If possible, do not keep paintings in places where they are exposed to unfiltered sunlight.
Exposure to Filtered Sunlight
Since most paintings are not stored outdoors, their sunlight exposure is usually in the form of filtered sunlight, which is less harmful than unfiltered sunlight. Even clear window glass serves as a filter that will block out the most damaging UV rays. However, filtered light can damage a painting. Sunlight will cause some colors of oil paint to fade over time and can also cause varnish to darken. Display artwork in a location that is not directly opposite a window or try to keep the shades or blinds drawn in rooms where oil paintings are on display.
Lightfastness of Pigments
If you have notice fading occurring in an oil painting, you might see that some colors seem to fade quicker than others. This is because some pigments are more lightfast than others. Each tube of paint is labeled with a lightfast grade. Paints labeled I or II are identified as archival quality as they are the most lightfast. They should not fade if a painting is properly cared for. Paintings with higher lightfastness grades are more subject to fading and some paints, such as fluorescent colors, are not lightfast at all.
Varnish is a clear protective coating that is applied to a painting after the paint has fully dried than can help protect it from light and dirt. An improperly applied varnish can lead to a painting becoming faded or discolored over time. Because it takes oil paintings anywhere from a few months to a year to fully dry, artists who wish to apply varnish will need to wait a considerable amount of time before they do so. Varnish may also be applied later by a collector to preserve a painting and to protect it against fading and damage. If applied too soon, varnish bonds with the paint and cannot be removed without damaging the painting. As a result, these paintings can become discolored and dull with age and there is little that can be done to restore them.