Bringing Colour To Our Lives

 

For most people, a life without colours is unimaginable. While humans can only see a relatively narrow band of the physical light spectrum, between 400 to 760 nanometres, the colours along this spectrum are important parts of our day-to-day lives. They provide us an understanding of the world around us, are symbols of various complex social and physical concepts, and can spark various emotions in us. It is no wonder, then, that the pigments responsible for these colours have also played crucial roles in human history. 

Natural dyes like Tyrian purple, indigo and cochineal, were so highly prized at various times in human history that people have set forth on expeditions, or even fought wars, to get these valuable dyes, each of which had a specific economic importance. In Ancient Rome, the highest-ranking nobility wore togas with Tyrian purple borders, as this was an expensive dye and hence considered suitable for their high status.

Similarly, one reason why the British colonised India was because it was a key exporter of indigo dye, which had a high export value. In many areas of Bihar and Bengal, the tinkathia system of indigo cultivation was a major cause of the impoverishment of the farmers, who had to sell two-thirds of their indigo crop to the government at statutorily fixed prices. This led to several rebellions by the indigo farmers, and also provided an impetus to protest literature and drama in Bengali. Colours indeed have a long and complex history, intertwined with several major world events.

With advances in science and technology, and natural dyes becoming increasingly expensive, artificial pigments also started becoming popular towards the end of the seventeenth century. There was also an epistemological shift, in art, from understanding colour as a mere reflection of nature to a more scientific understanding of the effects of colour on the eye. This in turn led to further progress on various artificial colours. Not only were these pigments available in a wider range of hues, but they could also be produced inexpensively, fulfilling the increasing demand for textiles in Europe.

As the Industrial Revolution gathered steam in the United Kingdom in the nineteenth century, fossil fuel burning generated particulate pollution that smothered the country and made green spaces increasingly hard to find. The market for artificial flowers and other reminders of the natural world, whether through colours, fashion, art or literature, expanded, and with it came the use of a new colourant that aimed to mimic the vivid green hues of a meadow or a forest. Scheele green, as it was called, after its inventor, became a popular hue for everything from wallpaper to furnishings to clothes. Even blancmange puddings were mixed with the pigment in parts of Scotland. 

However, there was a catch. Scheele green was made with an extremely poisonous arsenic salt. The poison often caused rashes and sores when people wore clothing dyed Scheele green, and it is rumoured that arsenic-laced wallpaper was a cause of Napoleon’s death. Tragically, many workers in the artificial-flower industry were also killed as a result of this poisoning, contributing to the decline of this sector, which had employed many women and children. 

In hindsight, one of the reasons for Scheele green’s popularity may have been its brightness and full saturation. From a neurological point of view, bright colours tend to capture our attention and activate reward-seeking mechanisms or strong emotions in our brains. It is for this reason that even now, many consumer goods and marketing campaigns use bright and highly saturated colours to attract customers.

This use of artificial colours for marketing is not without its consequences. In 2007, toymaker Mattel, manufacturer of toys such as Hot Wheels cars and Barbie dolls, was forced to recall four lines of toys after it turned out that their bright colours were a result of a Chinese contractor using highly toxic lead paint - narrowly avoiding a modern-day version of the Scheele green incident.

However, despite these past incidents, there have been some interesting new advances in artificial colours. A new blue discovered in 2009, YInMn Blue, is notably bright and stable under various conditions, and has even inspired a Crayola colour. There has been unexpected competition, too, over these artificial colours. The artist Anish Kapoor has sole rights to use a pigment made using carbon nanotube technology, which has been called the blackest black ever. In response, another artist, Stuart Semple, created another ‘superblack’ pigment and banned Kapoor from purchasing it.

More recently, researchers at Purdue University in Indiana have created a colour that is supposed to be the whitest ever, and has important implications for cooling buildings and mitigating the effect of climate change, as it radiates sunlight into space. This creates an interesting parallel with Scheele green, as the earlier artificial pigment was created as a response to climate change, that ended up killing people in its own right, while the new pigment aims to save lives by mitigating the effects of this climate change. In this way, colours and innovations in colour technology continue to play a huge role in our lives.

Image credits: Dan Brady, CC BY 2.0, via Wikimedia Commons