Colour story: Azo Yellow Green

Azo Yellow Green

From the history of pigments to the use of colour in famous artworks and emergence popular culture, every colour has a fascinating story. This month we explore the story behind Azo Yellow Green.

As a group, the azo dyes are synthesized organic pigments; they are among the brightest and strongest yellow, orange and red pigments, which accounts for their popularity.

Synthetic organic pigments have been used in works of art for over 130 years, but some early versions faded easily in light therefore many of the colours used by artists are no longer in production – these are called historical pigments.

Due to the lack of information on these historical pigments, it is challenging for conservators and art historians to care for these works, and several azo pigments are historical. This has only been compounded by artists who also experimented in making their own azo ‘recipes’, as Mark Rothko famously did.


"Rothko - Black on Maroon" by markhillary is licensed under CC BY 2.0
Rothko – Black on Maroon” by Mark Hillary is licensed under CC BY 2.0


Perhaps the most high-profile story of the detective work needed to restore a painting that used a historical azo is the story of Mark Rothko’s painting Black on Maroon (1958) which was defaced with black ink graffiti when it was on display at the Tate in London in 2012.

The restoration project took a team of experts two years to complete; in the process, they learned much more about the materials Rothko used and examined each layer closely so that they could remove the ink but preserve the integrity of the painting. Their work showed that the azo layer was affected by exposure to light over the years which, since Rothko was experimental in his use of materials and often created his own, was not surprising.