This week, there was a story in the news that brought the lighting industry and the art community a lot closer together. Some of the bright yellow colors in one of Vincent Van Gogh’s famous paintings were turning brown and, after much research, an international group of scientists revealed the cause: LED lighting.
Portrait of Gauguin. Source: http://www.vangogh.ua.ac.be
Since Leapfrog Lighting has art gallery customers, we took this research seriously and set out to investigate further. We have contacted the scientists who conducted the research and will post an update once we have all the information we require.
But in the meantime, let’s explore what we do know about LEDs and the reason art galleries and museums use them (for a complete examination, see the Kinsman Robinson Galleries customer story):
- LEDs are extremely energy efficient, long-lasting, and environmental-friendly, thus providing huge cost savings
- LEDs emit little to no heat, thus protecting valuable pieces of work from damage
- LEDs provide a clean, even light, bringing out the best in each work and displaying the work under the same type of light the artist produced it under and intended it to be viewed under (obviously, the quality of light can vary widely among manufacturers. For a better understanding of light quality, see Light quality of LED lamps).
- LEDs do not omit harmful UVs, which ultimately removes the risk of color degradation
It is this last point that made us confused about the scientist’s findings. It’s like being told the Earth isn’t round!
Based on the original research (which doesn’t provide all the information we require to make a proper assessment), the LED spectrum shown indicated that LED lights with a correlated color temperature (CCT) of over 6000K were turning a very specific chrome yellow paint color brown. The researchers also found that there are different types of chrome yellow, and that only the chrome yellow that contains a high content of sulfur was affected (the larger the presence of sulphur, the more unstable it is). Incidentally, the high sulphur chrome yellow is specific to only a handful of pieces from the late 19th century.
As described in the previous blog, Do LEDs have a color-rendering problem, CCT is essentially an indication of how red, yellow, or blue the white light is from a given lamp. CCT is measured in degrees Kelvin, of which blue is the hottest at 6000K and higher (sunlight is considered true white at around 6500K). If you have lamps that have a high Color Rendering Index (CRI), but a color temperature in the low end of the spectrum, art work might look less than desirable. This is why museums tend to use LEDs with high CCTs.
Interesting to note is that the scientists found that even under illumination considered safe, some test samples of chrome yellow started changing color. So it appears that high CCT LEDs do not stand alone as the only lighting technology to affect high sulphur chrome yellow paint.
If you find yourself with this unique combination, but don’t want to lose all the benefits associated with LED lighting, you might consider putting a blue filter in front of your high CCT LEDs so that it filters down to an incandescent or halogen spectrum. LED lighting is still the best lighting option for the extremely large majority of artwork on display.
If you have any additional questions or concerns, let us know!