Spotlight on Azo Yellow Green

From the history of pigments to the use of color in famous artworks to the rise of pop culture, every color has a fascinating story to tell. This month we explore the story behind azo yellow-green

As a group, azo dyes are synthetic organic pigments; they are one of the brightest and most intense yellow, orange and red pigments, which is why they are popular.

Synthetic organic pigments have been used in artwork for over 130 years, but some early versions fade easily in light, so many of the colors used by artists are no longer in production—these are known as historic pigments.

The lack of information on these historical pigments has made it difficult for conservators and art historians to care for these works, and several azo pigments are of historical interest. Artists also try to make their own azo “recipes,” as Mark Rothko is famously known, which only complicates the situation.

Perhaps the most striking story of the detective work required to restore a painting using historical azo is Mark Rothko’s painting Black on Maroon (1958) , which was defaced by black ink graffiti while on display at the Tate Gallery. London in 2012.

The restoration took a team of experts two years to complete; in the process, they learned more about the materials Rothko used and scrutinized each layer so they could remove the ink but maintain the integrity of the painting. Their work shows that the azo layer is affected by light over the years, which is not surprising given that Rothko has experimented with the use of the material and often creates his own.