Afterglow: A 1967 Rolex Submariner Reference 5512 With Tritium/Zinc Sulfide Markers
by Boris Pjanic
In the 1960s, tritium/zinc sulfide replaced radium/zinc sulfide as the lume of choice for watch dials and hands because, while still radioactive like radium, tritium is considerably less toxic.
Tritium’s half-life is 12 years, which basically explains why that substance will no longer glow strongly after 40 to 50 years.
I recall when I first found a Rolex Submariner 5512 with tritium/zinc sulfide on the dial. It led to a major discussion on an Internet forum about whether the dial had been re-lumed or not.
Well, years later, we know a lot more: the dial has not been re-lumed and,is was an original tritium/zinc sulfide dial.
A brief history of luminescence in watches
Lume: short for luminous phosphorescent, the substance that glows.
Phosphorescent: a type of photoluminescence, which unlike fluorescence, doesn’t immediately emit absorbed radiation, but emits it slowly. Zinc sulfide is phosphorescent.
Photoluminescence: substance that absorbs light (photons) and then re-radiates them, e.g. Super-LumiNova
1902-1960s: radium/zinc sulfide
The invention of radioluminescent paint can be attributed to William J Hammer, who mixed radium (in the form of radium salt) with zinc sulfide in 1902. Radium is radioactive (with a half life of 1,600 years) and emits alpha particles that energize the phosphorescent zinc sulfide, causing it to glow.
Radium-based lume was phased out in the 1950s/1960s as it caused radiation poisoning in those working with the substance.
1960s-1990s/present: tritium gas and tritium/zinc sulfide
Tritium replaced radium in the 1960s. Like radium, tritium is radioactive. However, it emits beta particles that are not as dangerous as radium’s alpha particles. Like radium, though, tritium was usually mixed with zinc sulfide, though a few brands, like Ball, have used small tubes of tritium gas that function like miniature, self-powered, bright-green fluorescent tubes.
Tritium has a half life (time taken for the emitted radiation to halve in intensity) of 12 years as compared to radium’s 1,600 years.
While zinc sulfide does glow for a short while after being exposed to light, tritium (and radium) lumes glow 24 hours a day as the zinc sulfide is energized by continuous radiation.
The brightness of the lume usually fades because the radioactivity gradually breaks down the zinc sulfide’s phosphorescent ability.
1990s-present: strontium aluminate/Super-LumiNova
Discovered in the early 1990s, strontium aluminate, also known by the brand name Super-LumiNova, glows 10 times brighter for much longer than previous lumes. It also odorless, non-flammable, and chemically and biologically inert so, not surprisingly, has come to dominate lume in watches.
The difference between strontium aluminate and zinc sulfide is that strontium aluminate easily absorbs and stores light (photons) so that it can be charged from either sunlight or artificial light. It doesn’t need a direct radioactive source of energy.
I recall when I first found a Rolex Submariner 5512 with zinc sulfide on the dial. It led to a major discussion on an Internet forum about whether the dial had been re-lumed or not.
Well, years later, we know a lot more; and one thing that is now certain is that the dial had not been re-lumed, but that it was an original zinc sulfide dial.
I myself have only seen two Rolex Submariner Reference 5512 models with this kind of luminosity, though just today I happened to see an Omega Speedmaster 145.022 with a zinc sulfide dial.
This is a first for an Omega wristwatch as far as I am aware.
But back to the watch at hand. The Rolex Submariner Reference 5512 went into production in 1959 with eagle-beak crown guards, which later became pointed crown guards before evolving into the rounded crown guards as we know them today.
Early versions are increasingly rare, the the tritium/zinc sulfide version even more so. Though there are no official numbers available, I estimate that there are probably just a couple hundred 5512 models outfitted with tritium/zinc sulfide that have survived.
The example shown here made its way from the United States to a collector in southern Germany and then to me.
Because it no longer had its original 7206 Oyster bracelet, I decided to put it on a Zulu strap, thus lending the unique dial a unique fashion look to match. It looks controversial, doesn’t it?
In their days, the Rolex Submariner 5513 and 5512 models were delivered with a so-called “superdomed” Plexiglas.
This type of hesalite crystal had a more rounded, domed shape to it as opposed to the later, flatter ones.
The superdomed crystal gave the watch a much different look, elongating the indices around the periphery. I love those superdomed crystals although they are supposedly not very water-resistant. But then I would not go diving with such a rare vintage piece anyway.
As you can see from the photo, the watch glows for a short time after being charged as if it were part of a German Christmas market.
The Reference 5512 with tritium/zinc sulfide has four lines of writing on the dial, with the lower two lines displaying a silvery grey-blue hue, not white.
I’m sure you can imagine that it is a lot of fun, although sometimes quite challenging as well, to research vintage Rolex timepieces to make sure they are original. The most important part for me is that the dial and hands match, fit into the correct time period based on the watch’s serial number, and that the dial “smiles” at me. Then you will see a smile sweep across my own face as well.
You can read much more from Boris Pjanic on his own blog, www.watchesandart.com.
Disclaimer: the author is a vintage watch dealer and any timepieces discussed may be for sale. For more information on him and his business, please read Meet Quill & Pad’s Vintage Virtuoso: Boris Pjanic, An Expert In ‘Pre-Loved’ Rolex.
*This article was significantly edited on December 23, 2014 to include historical information about lume and correct errors; “zinc sulfide” lume was replaced with “tritium/zinc sulfide” lume.
Reference number: 5512
Case: 316 steel, 40 mm, water resistance 200 meters (660 feet)
Bracelet: original steel bracelet Reference 7206 at delivery
Movement: automatic Caliber 1520 with C.O.S.C. certification
Functions: hours, minutes, sweep seconds
Price: new in 1968 was between $200 and $300. Current estimated value without matching steel bracelet around € 8,000 (approx. $10,000). Including matching bracelet estimated value around € 9,500 (approx. $13,000). This watch is too rare to be found at auction, therefore no auction results.
Trackbacks & Pingbacks
[…] 直到 1968 年，製錶廠便正式不再以鐳作為夜光塗料。在 60 年代，取而代之的新夜光塗層，則改用了氚（Tritium），氚的半衰期只有 12 年，毒性遠低於鐳，唯一相應的缺點就是 40 到 50 年之後，夜光效果便會減退或消失。但當然，對人體的壽命來說，不奢望永恆，時效已經足夠。 […]
[…] more on luminous substance, see Afterglow: A 1967 Rolex Submariner Reference 5512 With Tritium/Zinc Sulfide Markers and How We Realized Putting Radium in Everything Was Not the […]
[…] To read Boris’s first article for Quill & Pad, please see Afterglow: A 1967 Rolex Submariner Reference 5512 With Still-Radiant Zinc Sulfide Markers. […]
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Very confused by this story. There is no such thing as pure tritium paint –tritium is an isotope of hydrogen; it’s a gas at room temperature. My understanding is that it’s _always_ mixed with zinc sulfide when you use it for luminous paint. You can’t have pure tritium paint, it’s a physical impossibility. The only way you can use straight tritium for lume is to put it in a sealed glass tube, a la Ball Watches. Can you guys clarify exactly what the author’s meaning is here?
Hi Jack, I’m confused by your comment as I see no reference to pure tritium, or pure tritium paint, at all in the article, but I do see “zinc sulfide” in both the title, the first paragraph, and zinc sulfide is referenced throughout the article.
p.s. My understanding is the same as yours in that tritium compounds are mixed with zinc sulfide to form a glow-in-the-dark paste.
The article clearly says there are “zinc sulfide” versions (supposedly) of tritium dials. As you say, there is as far as we know, no such thing as a _non_ zinc sulfide version of tritium dials –it is a standard additive in tritium based luminous paint. The article seeks, as I read it, to draw a distinction between tritium-only dials (and as we seem to both agree there is no such thing) and tritium dials treated with zinc sulfide; however there is no such distinction to be drawn. Thoughts?
Incidentally, Ian, of course the article does refer to “pure tritium:”
“Without seeing the watch glow, it can at times be difficult to recognize exactly what it is. What I found out is that the markers tend to have a greenish lume color as opposed to the more vanilla or white tones of pure tritium.”
Thank you for the article it has given more information than I have acquired from the Rolex service center in NYC. I have a 1960s Tritium Rolex with stainless steel bracelet and a Women’s Gold Lapel Rolex, which was made into a women’s wrist watch. The Rolex service center quoted the Men’s Submariner to be higher than you advertised. As for the women’s gold lapel Rolex they could not place a value since it was one of the first women’s Rolex that Rolex had put it’s name on.
Thanks for this article! I seem to have inherited a 5512 from my father. It definitely has the traits of Tritium/Zinc Sulfide described (charged with light, it has a green glow and fades out in less than a half hour). I don’t care how much it’s worth, I’d never part with it.
One cool thing, my father saved the original ad from 1967. Maybe he got it with the watch, I’m not sure. If you all would be interested, I’d happily post it.
Thanks for your comment Mark and please do post a photo of the original advertisement.
Mark, I messaged you in private, feel free to send pictures…
HI I HAVE MY FATHERS 5512 SERIAL NUMBER 691991 THE DIAL GLOWS THE HANDS DO NOT IS THIS CORRECT? ALSO THERE IS NO SWISS NAME AT 6:00 ? HE MUST HAVE HAD THE BAND CHANGE ITS STAMPED 1-72. HE PURCHASED THE ROLEX IN CURACAO, NETH, ANT. I WOULD APPRECIATE ANY INFORMATION . THANKS ALAN P.S LOOKING FOR THE 7206 BAND.
Hi Alan, I emailed you. Feel free to respond.
Can the dial be a prototype because it does not have Swiss at 6.?
Hi Boris did the girls who painted the dials sign the of the dial? Mine has BB 359 thanks Alan
Have my father 5512 with pointed guard. The dial numbers has a greenish color. It glows for about 1 minute. It does not have Swiss at 6. Can this dial be a prototype? Dial was never touched. Had watch since new. Thanks for your help
These zinc sulfide watches are interesting and rare! I would love to have some “rough” numbers to how many were produced because I have a really fine 1968 GMT Master with a Zinc Sulfide dial. Hopefully, the future will shed some light on just how “rare” these examples are. Thanks for the article!
I’m not sure he has all the facts. Rolex as far as I know switched from a zinc sulfide\radium mix to zinc sulfide\tritium around 1963. Early 60’s Submariner had a dot at the 6:00 rail mark signifying the switch to the new Atomic Energy Commission regulations requiring lowering the emissions through the use of tritium but to my knowledge there has never been a zinc sulfide only dial. Feel free to bring evidence to correct me.