By James Aitchison

It all began in 1775 when Swedish chemist Carl Wilhelm Scheele invented a stunning new pigment — a green more vibrant, more luminous, than anything seen before.  The secret?  The miraculous new pigment was copper arsenite, also called acidic copper arsenite, which tragically contained the chemical element arsenic.  As did canary yellow, another new eye-catching — and deadly — hue.

Scheele’s green, as it became known, took the world by storm.  Green rooms became the “in” thing.  Especially in Britain, where the emerging middle-class loved it.  It found its way onto wallpapers, paper furniture linings, textiles, cloth-bound book covers, clothing, paint, and even children’s toys.  By the dawn of the nineteenth century, Scheele’s green had replaced the older (and safer) green pigments based on copper carbonate. 

A glimpse into its manufacturing process should have rung alarm bells.

Bring a solution of sodium carbonate to a temperature of around 90°C, then slowly add arsenious oxide, which is highly toxic to humans, a carcinogen, and dangerously corrosive.  By stirring until everything has dissolved, the result is a sodium arsenite solution.  Then, combining it with a copper sulfate solution, a green substance of insoluble copper arsenite is obtained.  After filtration, the product is dried at about 43°C.  To enhance the colour, add salt heated to 60-70°C.  The copper-arsenic ratio determined the intensity of the green.  Scheele’s beautifully vivid green was composed of a variety of different deadly compounds, including copper arsenite salt, copper arsenate, and copper diarsenite.  It was, in every sense, a killer colour.

Scheele’s green led to one of the greatest mysteries of the nineteenth century.  English middle-class families were succumbing to an invisible toxic poison.  Queen Victoria was not amused!

No one suspected the toxicity of an arsenic compound.  Newspapers of the day carried reports of “children wasting away in bright green rooms, ladies in green dresses swooning, and printers overcome by deadly vapours”.  At a Christmas party where dyed candles burned, children were “acutely poisoned”.

Wallpaper was the prime culprit in English middle-class homes.  Tiny particles of the arsenic pigment flaked off and, once airborne, were absorbed by the lungs.  As well, toxic gases were produced from compounds containing arsenic when the room was heated.  And should the wallpaper become damp and mouldy, the pigment released poisonous arsine gases.  Fungi, it seems, always release arsine gas when they grow on a substance containing arsenic.  Given Britain’s damp climate, fungus growing on wallpaper was a silent killer.

To make matters worse, William Morris, the British writer and designer, and a founder of the Arts and Crafts Movement, championed the use of Scheele’s green and other arsenic-based pigments.  He created fifty different wallpapers with intricate, stylised patterns celebrating the native flowers and plants of Britain.  

Morris was a perfectionist, designing the most famous British wallpaper of the nineteenth century.  His wallpapers used pieces of paper thirty feet long and twenty-one inches wide.  A different wooden block applied each colour.  Some designs demanded sixty-eight different blocks.  When one colour had dried on the paper, the next colour was printed over the first.  Small wonder it took as long as four weeks to produce a single set of wallpaper designs. 

Morris had no compunction about using arsenic-based pigments.  After all, his father’s company was the largest arsenic producer in the world.  (Morris Senior was a shareholder in the Devon Great Consolidated Copper Mining Company, once the world’s most productive copper mine.  Over time, the quality of the copper ore yielded more arsenic than copper.  So, the company switched to profitably refining arsenic.)  

Wallpaper became a ticking time bomb in many homes.  It’s hard to picture it nowadays, but Victorian middle-class homeowners used several different wallpapers in the same room!  It was considered the height of good taste.

By the mid-nineteenth century, the mysterious illnesses and deaths attracted closer medical scrutiny.  One doctor, Thomas Orton, was determined to find out why all four children in one family had succumbed to the same unexplained sickness.  He began investigating their home and contents; he found nothing wrong with the home’s water supply or its cleanliness, but a room of bright green wallpaper brought to mind an unsettling theory: could wallpaper kill?

Despite mounting evidence, Morris refused to accept that arsenic-based pigments were killers.

He avowed that the arsenical wallpaper in his own home had not caused him to get sick.

As newspaper reports increasingly condemned arsenical wallpapers, the public turned its back on them.  Eventually, Morris was forced to stop using arsenic. 

In 1885, a thoroughly unrepentant Morris declared to a friend: “As to the arsenic scare, a greater folly is hardly possible to imagine.  The doctors were bitten as people were bitten by the witch fever.”

By the end of the nineteenth century, cobalt (zinc) green replaced Scheele’s green.  Ironically, by the 1930s, Scheele’s killer green had found a new home: in insecticides.