In the mid-1920s, in a brick factory building in Orange, New Jersey, young women would sometimes paint their fingernails, their teeth, even their faces, with the same pale paint they used all day on watch dials. In the dark, the effect was delightful — a soft, otherworldly green glow that their friends and families found genuinely enchanting. The women who worked there were nicknamed, half-affectionately, the “Ghost Girls.” None of them knew they were poisoning themselves with every brushstroke.
To understand why that paint existed at all, you have to go back further — to the trenches of the First World War. A First World War handbook for officers going to the front, Captain Lake’s Knowledge for War, put a “luminous wristwatch with unbreakable glass” at the head of its kit list. Soldiers needed to coordinate attacks to the minute, in total darkness, without striking a match that would give their position away to a sniper fifty yards off. Omega, Longines, Elgin, Rolex, and Waltham all produced military wristwatches through the war, most of them fitted with radium-painted hands and a handful of radium dots on the dial. It is not an exaggeration to say that the modern wristwatch, as an object every soldier and then every civilian simply wore rather than carried, owes a meaningful part of its rise to this one wartime necessity: a dial you could read without lighting anything at all.
Realistic illustration of a First World War officer’s wristwatch with radium-painted hands and numerals, readable in total darkness. An imagined scene.
Radium itself had been discovered by Marie and Pierre Curie in 1898, and it took commercial chemistry less than two decades to turn a scientific curiosity into an industrial product. The Radium Luminous Material Corporation, later renamed the United States Radium Corporation, began manufacturing luminescent paint in 1914. Two years later, Ingersoll launched its “Radiolite” watches, and the glowing dial — once a novelty — became something close to a standard feature. One of the people credited with inventing the paint, Sabin von Sochocky, died of aplastic anemia in 1928, a blood disease of the kind radium is known to cause.
Part of the reason so few people feared it is that, for a generation, radium had been sold as good for you. Pharmacists had argued since the 1910s that tiny doses stimulated living cells, an idea that was never demonstrated, and shops sold radium water, toothpaste and tonics; the most famous of them, Radithor, was drunk in large amounts by the American golfer and industrialist Eben Byers, who died of radium poisoning in the early 1930s. In France, pharmacies began selling Tho-Radia in 1932, a face cream made with thorium chloride and radium bromide, followed by a powder, a soap and a toothpaste. Its poster, designed by the publicist Tony Burnand, showed a young woman lit from below by a beam of rays, and its label read “according to the formula of Dr Alfred Curie”. He was a real physician, but no relation of Marie and Pierre Curie, who reportedly considered legal action. A laboratory certificate of 1932 put the radium at a fraction of a microgram per 100 grams of cream, and that was the pitch: small doses stimulate, large ones destroy. In 1937 France classified radium and thorium as toxic, to be sold only on prescription and under a “Poison” label. The brand carried on without mentioning radium or Curie and faded from the market in the 1960s; whether its later products still contained any radium is unclear.
Realistic render based on a French advertisement for Tho-Radia face cream, mid-1930s.
The chemistry behind the glow is, once you see it, elegantly simple. Radium-226 decays by emitting alpha particles — small, energetic, and essentially harmless from the outside, since they can’t even get through a sheet of paper, let alone human skin or a watch crystal.
Illustration of how radium luminous paint works: alpha particles from radium-226 strike zinc sulfide crystals, which release the light.
Mixed into the paint alongside the radium was a phosphor, almost always zinc sulfide, doped with trace amounts of copper or silver. Every time an alpha particle struck a phosphor crystal, it knocked an electron up to a higher energy state; the electron’s fall back down released that energy as a small packet of visible light. Billions of these tiny collisions, happening every second across the dial, add up to a continuous, self-powered glow — one that needs no sunlight, no charging, nothing at all except the radium’s own decay. Because radium-226 has a half-life of about 1,600 years, that glow was, for practical purposes, meant to last forever.
It very nearly did — but the people painting it on did not.
Realistic illustration of a dial painter shaping her brush with her lips before dipping it in radium paint, the technique supervisors called “lip, dip, paint”. An imagined scene.
The work itself was almost absurdly delicate for an industrial process. Supervisors taught the women a technique the industry euphemistically called “lip, dip, paint”: shape the brush’s bristles to a fine point between your lips, dip it in the radium paint, apply it to the dial, and repeat — thousands of times a day, for a wage of about a penny and a half per dial. By one account, roughly a thousand women at the Radium Dial Company’s plant in Ottawa, Illinois, were producing something like 4,300 dials a day at the peak of production in 1925. Across the United States Radium Corporation’s New Jersey plant, the Radium Dial Company’s plant in Ottawa and a third site in Waterbury, Connecticut, close to 4,000 women would eventually do this work. They were told, repeatedly and falsely, that the radium was present in such tiny quantities that it was essentially harmless. Some even used it as makeup for a party, delighted by the strange, cold light it threw.
Realistic illustration of women dial painters at work in a 1920s watch dial factory. An imagined scene.
Radium is chemically similar enough to calcium that the body cannot tell the difference. Ingested in the quantities these women were swallowing — not from any single dangerous dose, but from thousands of small, deliberate brush-pointing a day — it settled permanently into their bones and simply stayed there, irradiating them from the inside for the rest of their lives. The results, when they came, were horrifying and specific: necrosis of the jawbone so severe that dentists could lift pieces of it away with their fingers (the condition became known, grimly, as “radium jaw”); crippling anemia; spontaneous fractures; sarcomas; sinus cancers.
By 1927, more than fifty of the women who had worked in these factories were dead.
It took a remarkably small number of people, pushing hard against a great deal of institutional resistance, to connect the deaths to the dial-painting work at all. Dr. Harrison Martland, the county physician of Newark, began linking a cluster of mysterious deaths — including that of the United States Radium Corporation’s own chief chemist — to radium poisoning around 1925. Cecil and Katherine Drinker, two researchers from the Harvard School of Public Health, inspected the Orange, New Jersey plant in the early 1920s and found an environment saturated with radioactive dust and no protective measures of any kind. When the company’s president, Arthur Roeder, saw a draft of their findings, he threatened legal action and quietly submitted an altered version of the report to the New Jersey Department of Labor. It was the pioneering industrial toxicologist Alice Hamilton who discovered the company had tampered with the Drinkers’ own data — and who made sure the real findings reached the public.
The legal reckoning that followed took years and, for most of the women involved, came far too late. In New Jersey, five women — Grace Fryer, Edna Hussman, Katherine Schaub, Quinta McDonald, and Albina Larice — spent two years searching for a lawyer willing to take on the United States Radium Corporation before finally filing suit. By the time they appeared in court in January 1928, two of the five were bedridden, and none of them could lift an arm high enough to be sworn in in the conventional manner. They settled that year for $10,000 each (something over $180,000 today) plus a $600 annual annuity for as long as they lived, with medical and legal costs covered. All five were dead by the 1930s.
Realistic illustration of the legal fight of the Radium Girls against the United States Radium Corporation and the Radium Dial Company in the late 1920s and 1930s. An imagined scene.
In Illinois, the fight took even longer. Catherine Donohue, who had worked at the Radium Dial Company’s Ottawa plant, became too ill to travel to her own hearings; the Illinois Industrial Commission eventually took her testimony at her home. A local attorney named Leonard Grossman represented Donohue and four other women without charging a fee — his clients, by that point, had no money left to pay him. The commission ruled in the women’s favor in the spring of 1938. Radium Dial appealed all the way to the United States Supreme Court, which finally declined to hear the case on October 23, 1939, letting the ruling stand. Catherine Donohue had died before a single payment reached her family.
There is a final, bitter footnote to the Illinois story that most short accounts leave out. After Radium Dial’s dissolution, its former head, Joseph Kelly, opened a new company, Luminous Processes Inc., a few blocks away in the same town of Ottawa — and kept painting radium watch dials there until 1978. It was among the last radium dial factories operating in the United States, more than fifty years after the dangers had first become public knowledge. Radium was never banned outright by a single piece of legislation; the industry simply, slowly, abandoned it as tritium became available and as the reputational and legal cost became impossible to ignore.
What the Radium Girls’ cases did accomplish was broader than any one settlement. The litigation helped establish, for the first time in American law, that an individual worker could sue a corporation for damages caused by conditions the employer knew about and concealed. Data gathered in 1933 by the MIT physicist Robley Evans, measuring radon exhalation and radium excretion in surviving former dial painters, went on to inform the first national radiation safety standard in 1941. In 1968, the Center for Human Radio-biology was established at Argonne National Laboratory specifically to continue studying the survivors; by the time it concluded in 1993, it had documented 2,403 cases. The women’s story has since been told in Kate Moore’s bestselling book “The Radium Girls” and dramatized in a 2018 film of the same name, starring Joey King — a reminder that this history has never entirely faded from public memory, even if the dials themselves eventually did.
Realistic illustration of a surviving dial painter being measured in a steel-walled whole-body counting chamber, of the kind used in the long-term studies of the Radium Girls’ survivors. An imagined scene.
Tritium, which gradually replaced radium in Swiss watchmaking from the 1950s onward, was a genuine improvement, if an imperfect one. As a beta emitter, tritium’s radiation is far weaker and far less penetrating than radium’s — it can’t travel more than a few millimeters through air and poses negligible external risk. Just as important, tritium doesn’t behave like calcium in the body, so it doesn’t settle permanently into bone the way radium does. For about three decades, it was the default for nearly every luminous dial made. (A beta-emitting alternative called promethium-147 saw brief, limited use in the 1960s — unlike radium, it didn’t degrade the phosphor it was mixed with, but its short, 2.62-year half-life made it impractical for anything meant to glow for more than a few years.)
Tritium came with its own regulatory paper trail, one still visible on watch dials today. A small “T” printed near six o’clock simply means the dial contains tritium-activated material, and “Swiss T<25” indicates Swiss manufacture and a tritium content below 25 millicuries.
Realistic render based on a documented example of a watch dial marked “SWISS T<25”, the Swiss designation for a tritium content below 25 millicuries.
A stricter designation, “T Swiss T”, means the content is below 7.5 millicuries. If you’ve ever wondered what those small letters mean on a 1970s dial, that’s your answer.
Realistic render based on a documented example of a dial marked “T SWISS T”, indicating a tritium content below 7.5 millicuries.
Tritium’s own radioactivity, however modest, eventually caught up with it too: in 1998, Switzerland prohibited its use in watchmaking altogether, by which point an entirely different kind of solution had already arrived.
That solution is the compound most new watches use today, known commercially as Super-LumiNova. It was developed by four scientists — Yoshihiko Murayama, Nobuyoshi Takeuchi, Yasumitsu Aoki, and Takashi Matsuzawa — working for the Japanese firm Nemoto & Co., a luminous-paint specialist founded back in 1941. Their invention, patented in 1994, is built on strontium aluminate doped with europium and dysprosium, and in 1998 — the same year Switzerland banned tritium dials — Nemoto formed a joint venture with the Swiss firm RC Tritec AG to produce it as “100% Swiss made” Super-LumiNova for the watch industry.
Realistic illustration of a Super-LumiNova dial glowing in the dark after being charged by light.
The mechanism is the real break with everything that came before. Super-LumiNova contains no radioactive material whatsoever. It is photo-luminescent rather than radio-luminescent: expose it to ordinary light — sunlight, a lamp, a camera flash — and its electrons absorb that energy, then release it slowly as visible light over the following hours. It is, in a sense, a battery rather than a generator. For eighty years, the light on a watch dial had come from something ancient, decaying quietly and permanently inside the paint, asking nothing of the wearer and giving nothing back once a case was sealed. The light we borrow today has to be returned, recharged, and borrowed again — a small, constant reminder, if you choose to read it that way, of exactly what it cost to make that light safe in the first place.
A short, practical note for collectors
If you own, or are considering buying, a genuinely vintage watch, there’s a reasonable chance its original lume is one of these three materials, and it’s worth knowing which. Pre-war and immediate postwar pieces, with no dial markings and lume that has typically stopped glowing entirely (the zinc sulfide phosphor itself burns out under decades of radioactive bombardment, even though the radium underneath remains essentially as radioactive as the day it was applied — the glow dies; the radioactivity does not), are almost certainly radium.
Realistic illustration of the dial of a vintage watch with aged radium lume that no longer glows.
Dials marked “T,” “Swiss T<25,” or “T Swiss T,” generally from the 1960s through 1998, are tritium. Tritium has a half-life of about twelve years, so the glow on most of these dials has long since faded, even though the markings remain. Anything unmarked and brightly reactive after a moment under a lamp is almost certainly a modern replacement or a watch built after 1998.
None of this should alarm anyone who owns one of these watches. An intact radium dial, in a closed case, on a wrist, is not a meaningful hazard — alpha particles can’t get through a watch crystal, let alone human skin, and gamma emission at that quantity is negligible at arm’s length. The real risk only appears if a case is opened carelessly, old lume is scraped or flakes loose, or several such watches are stored unventilated for years in one small space. If you’re ever having a radium-dial piece serviced, it costs nothing to simply tell your watchmaker what’s on the dial before they open the case.
That history is part of why restoration means something different to us than it might elsewhere. A number of the pieces in our Art Deco collection came to us originally fitted with radium dials — the same material, the same decade, the same industry this whole story describes. Rather than leave a radioactive dial untouched for the sake of “originality,” or quietly swap it for something generic, we restore each one by hand with Super-LumiNova, recreating the original numerals and dial design as closely as the records and the piece itself allow, so the watch looks and glows the way it was meant to — just without carrying a century-old health risk on your wrist.
It’s a small, specific way of taking this history seriously: not erasing it, and not ignoring it either.