'I was asked to paint dials," 15-year-old Katherine Schaub wrote in the spring of 1917, just as the United States was entering the First World War. "I said I would like to try it."
Dial-painting was the hot new profession for working-class women in the US: a lucrative, artistic and glamorous job that gave the mostly young employees a chance to work with the recently discovered wonder element, radium, as well as "do their bit" for the war effort.
They used luminous radium paint to make the numbers on watches, clocks and aeronautical dials glow brightly in the dark. And they were instructed to suck their paintbrushes, to make a fine point for the precise handiwork.
Speaking to a lawyer years later, dial-painter Mae Cubberley remembered: "The first thing we asked was, 'Does this stuff hurt you?' But [my boss] said no. He said that it wasn't dangerous."
That wasn't true. Radium was known to be hazardous - other employees, handling larger amounts, wore lead aprons - but the radium firms insisted that small amounts were beneficial to health. In fact, a whole industry was built around this claim.
As preposterous as it sounds today, retailers in Britain and America sold dozens of grocery products, such as butter, milk and chocolate, that had been laced with radium to improve customers' wellbeing.
Shoppers in British stores were sold radium-infused face creams, eyeshadows, soaps and lipsticks that promised to make their beauty "really shine". There were radium energy tablets and even radium-laced lingerie to improve consumers' sex lives.
Manufacturers funded research that supported their claims - and ignored independent studies that proved the opposite. So when the dial-painters asked their bosses if it was safe to lip-point, they said yes. They told the girls that radium would make them good-looking. So the women picked up their brushes and placed them in their mouths - over and over and over again.
I knew nothing about this shocking story until two years ago, when I was asked to direct a play about the so-called "radium girls" and their long fight - in the face of deadly radiation poisoning - to force their employers to admit negligence.
The show - These Shining Lives by Melanie Marnich - played in fringe venues in London, but I felt the women's battle for justice deserved a wider audience. I resolved to piece together the full sequence of events and now, after an extensive research trip to America - where I tracked down and interviewed the women's families and gained unprecedented access to diaries, letters and court testimonies - my book is about to be published.
The women's story begins in Newark, New Jersey.
Four years after the First World War, 24-year-old Mollie Maggia, a former employee at a dial-painting factory, died what her sister called "a painful and terrible death". She was the first factory girl to die, but others followed, and more women began to feel sick. Katherine Schaub's teeth started falling out - they looked "moth-eaten", dentists said. Other dial-painters began to suffer spontaneous fractures.
Yet the doctors the women consulted were perplexed. With radium viewed as a wonder drug, the toxic element was not believed to be at fault. Then, in 1925, a pioneering doctor, Harrison Martland, proved the connection between the women's work and their illnesses after discovering that radium had deposited in the women's bones.
This diagnosis should have resulted in the suspension of dial-painting nationwide. But the radium firms were making far too much money to allow the fate of a few lowly dial-painters to disrupt business.
"I still feel that we have to find the cause," wrote Arthur Roeder, president of the United States Radium Corporation. The companies were adamant they would accept no responsibility.
In New Jersey, the women's illnesses had an understandable effect on the profession's popularity: dial-painting declined. But 800 miles away in Ottawa, Illinois, where a new studio had opened, the painters were unaware of the problems - and their employers did not inform them of the now-established danger.
Something had to be done. Grace Fryer was the dial-painter most committed to the cause: a principled young woman, she battled for years to find a lawyer who would take their case. In 1928, Grace, Katherine and Mollie's sisters Albina and Quinta finally faced the firm that had poisoned them in court, filing a lawsuit for $250,000 each (equivalent to $3.4m today).
Their case was brought by a young lawyer just out of Harvard, Raymond H. Berry, and it made international headlines. Though these women were persuaded to settle out of court - they had been given only months to live - their lawsuit had major repercussions, not just in New Jersey, where it led to improvements in worker-safety laws, but nationwide. For, at last, the dial-painters in Ottawa learnt of the danger.
"The girls became wild," remembered one, Catherine Wolfe. "The chill of fear was so depressing we could scarcely work."
But their employers at Radium Dial even now reassured them that their work was safe, telling the Ottawa women there was no danger because they used a different type of radium. By the time the Illinois women tried to file suit, Depression had gripped America. Despite the evidence against Radium Dial, no one was in the mood to hold to account one of the few employers left who had not gone bankrupt. Wolfe and her friends were shunned by their community for seeking justice.
They signed with Leonard Grossman, a 46-year-old lawyer who, according to his son, "had a passion for people who were in trouble". With Grossman's assistance, the women finally won their case in 1938. The judge condemned the radium company for "gross negligence".
In their fight for justice, the dial-painters faced powerful opponents who betrayed and lied to them. Their determination to stand up for their rights lead to many legal changes that protected other workers.
Katherine Schaub, the 15-year-old girl who had been so excited to pick up her paintbrush in 1917, had dreamt of becoming a famous writer when she grew up, but fate had a different kind of fame in store for her. She died in 1933, aged 30. Her courage and sacrifice shines brighter through history than any luminous dial.