Watchmaker question about old dial glow material

[iwc3]

I'm a watchmaker who specializes in refinishing old and new dial adding luminescence to dial numbers and hands. Normally I use blends of strontium aluminate to make the dials glow. However, I have a question about a very old dial I am trying to repair.

 

The dial was originally made with two glowing substances. One was tritium which has long ago lost its "glow". They also mixed the tritium with a phosphorescent material that absorbed light and glowed for a minute. I'm trying to identify the compound that glowed brightly after a charge and withing about 30 seconds lost most of its glow. I have heard watchmakers used Zinc Sulfide before what they use now. However, I don't think it was ZnS. I don't know enough about phosphorescent compounds to consider anything else.

 

Here's the question I have:

Is there a compound that upon having been "charged" in daylight or under fluorescent light, it glows brightly and quickly, within 30 seconds loses most of its glow?

 

I uploaded a video of another dial just like the one I am trying to repair showing the "complete one" in daylight, and turning off the light to show how it glows but quickly diminishes. The video is of a 100% original dial that demonstrates how the old tritium no longer glows, but the phosphorescent material still works. Its a Rolex dial from the 60s. I am repairing another dial like it. The best we can figure is Rolex used "Tritium" for the main glow properties, and they used this Phosphorescent material to give the dial markers a "quick glow", but it didn't last long.

 

Thanks for all your help.

Kent

IMG_68412.MOV

Edited November 28, 2012 by iwc3

[Phi for All]

I thought radium was the element of choice for glowing watches through at least the 60s. AFAIK, any phosphorescent material (calcium sulfide, strontium sulfide) can be used in conjunction with the radium or tritium, since that's what provides the energy for the phosphorescence to continue.

 

Iirc, radium has an outrageous "glow-life" (like over a thousand years) but isn't bad as long as you don't ingest it in any way (one of our members thought some might have been spilled on the floor of the home he rents). The amount of radiation from a watch would be harmless, but not undetectable. Wasn't it a Rolex that James Bond used to test his Geiger counter in Dr. No?

[iwc3]

Radium was used from the 1910s to about 1960. Rolex used it til 1960 in their watches, at which time they switched to tritium. I recall hearing about 007 and his watch. It was definitely an old Submariner. I think you're right about the geiger counter.

 

There is a story about the "Radium Girls". Around 1917 in New Jersey a group of girls were hired to paint watch dials with radium. They were told it was harmless, and they routinely licked their brushes they used to apply it and some even had fun painting their teeth and showing off to their boyfriends their "glowing smiles". Many of them contracted radiation poisoning. Eventually there was a lawsuit on their behalf.

 

I've worked on a lot of WWII watches and airplane clocks with radium applied to the dials.

 

Do you think calcium sulfide or strontium sulfide might be compounds I could obtain and make into a fine powder to apply and give my dial numbers that "quick" and short lasting glow?

Edited November 28, 2012 by iwc3

[Externet]

For the 'old' part, I bought 40 years ago, and still have, a kit like this, but the box is orange color and marked "Radium"

 

It behaves as you say about the luminosity, charging by light and losing its 'charge' in about a minute. Perhaps that is what you are asking for ?

 

----> http://www.orau.org/ptp/collection/radioluminescent/favoritetouchupkit.htm

Edited November 28, 2012 by Externet

[iwc3]

Wow, what a piece of history, Back in the 70s in watch repair school, they gave us a kit to paint indices. It was something like that. It makes sense to me now what "Phi for all" said about mixing the two materials. I could see how the Radium or Tritium would assist the phosphorescent material to continue glowing as well. Very interesting.

 

My task at hand now is to repair the dial indices with a mixture of "non-glowing" materials that look like aged tritium (this I have done) and to also blend in a short glowing light charged compound, much like strontium aluminate that I use now, but something that has a very short glow time.

 

Any suggestions on that?

For the 'old' part, I bought 40 years ago, and still have, a kit like this, but the box is orange color and marked "Radium"

 

It behaves as you say about the luminosity, charging by light and losing its 'charge' in about a minute. Perhaps that is what you are asking for ?

 

----> http://www.orau.org/...etouchupkit.htm

[John Cuthber]

My guess is that the original was based on this stuff

http://en.wikipedia.org/wiki/Zinc_sulfide#Luminescent_material

 

It's important to realise that the glow may have faded over the years but the radioactivity will not have.

The stuff is just as big a radio-toxic hazard as it ever was (if not more so, from the daughter products)

 

The radiation from the radium damages the phosphor and so those bits stop glowing. The range of the radiation is tiny- well under a millimetre- and so most of the phosphor is out of range of the radiation. (The radium is never perfectly mixed into the of the phosphor, it's in tiny lumps.) The rest of the phosphor still works so it still glows faintly for a short while after you turn the lights off.

Edited November 28, 2012 by John Cuthber

[StringJunky]

From a decorating site:

 

Phosphorescent or luminous paints may themselves be sub-divided into two classes-those which give a relatively bright afterglow of short duration and those which give a longer but less bright afterglow.

For the first class, zinc sulphide or zinc and cadtnium* sulphide are the pigments most employed; for the second, calcium sulphide, strontium sulphide, or combinations of the two, are commonly used.

The medium may be oil or cellulose varnish.

 

All pigments for phosphorescent paints are comparatively coarse in particle size, since the property of phosphorescence depends mainly on a coarse, crystalline structure; consequently they cannot be ground in a tightly-set roller mill.

Either a very loosely-set mill must be used or the pigments must be stirred or mixed in the medium.

The range of colours in which they are available is limited to a greenish-yellow phosphorescence for the first class, and a bluish green for the second; in daylight, the colour is a dull white.

 

Owing to their coarseness, phosphorescent paints have poor gloss, do not flow well, and tend to settle hard and quickly.

Best results are obtained if they are applied over a white-base coat, such as a good zinc white; on no account must the undercoat contain any white lead, - either as a pigment or in the form of a drier.

For outside exposure, the luminous paint must be protected by a coat of clear varnish or lacquer, or it will soon disintegrate.

The protective coating will involve some loss of luminescence.

 

* I think this should read cadmium

 

http://www.bozzle.com/paintluminous.html

Edited November 28, 2012 by StringJunky

[iwc3]

Thank-you John and Stringjunky. I've learned quite a bit already. Maybe the phosphor was Zinc Sulphide. Now I'm trying to find some "white" Zinc Sulphide powder that will allow me flexibility in making my beige to yellow beige mixes.

 

Also, I have noticed when I crush my phosphors compounds down to smaller than 30-40 microns, they lose some of their glow potential.

 

iwc3

[StringJunky]

Thank-you John and Stringjunky. I've learned quite a bit already. Maybe the phosphor was Zinc Sulphide. Now I'm trying to find some "white" Zinc Sulphide powder that will allow me flexibility in making my beige to yellow beige mixes.

 

Also, I have noticed when I crush my phosphors compounds down to smaller than 30-40 microns, they lose some of their glow potential.

 

iwc3

 

I think the light-capturing ability is a property of the particle size...the bigger the particle in the powder the 'faster' it is. It's similar to camera-film emulsions...the faster the film (more light-sensitive) the grainier the final picture due to the bigger grains.

 

I don't know where you are but I found glow-in-the-dark powder which uses zinc sulphide from the US:

 

http://www.stevespanglerscience.com/product/1586#review

 

Edited November 28, 2012 by StringJunky

[swansont]

FWIW, if the dials used radium or tritium, as Phi alluded, the phosphor's glow wouldn't have to last long, as the material would be constantly refreshed, as it were. Tritium has a half-life of 12.3 years, so if this is an older watch, from the 60's, that means it's gone through ~4 half lives, so the tritium's activity has dropped by a factor of 16. Even if the phosphor is intact, you wouldn't get much of a glow from the tritium.

 

Whatever is used in kids playthings, like the stars you can affix to a ceiling, glow for several minutes (if they're decent ones, at least). As you noted, ZnS is a common phosphor; when you add Cu impurities, it lasts a while. Strontium aluminate is another candidate. Wikipedia says "it is about 10 times brighter and 10 times longer glowing, however about 10 times more expensive than ZnS:Cu" and that it's what's in a lot of kids' GITD toys.

 

http://en.wikipedia.org/wiki/Strontium_aluminate

[iwc3]

Looks like that is what I need. I live in Flagstaff, AZ. I just ordered some. Thank-you String Junky.

 

Iwc3

I think the light-capturing ability is a property of the particle size...the bigger the particle in the powder the 'faster' it is. It's similar to camera-film emulsions...the faster the film (more light-sensitive) the grainier the final picture due to the bigger grains.

 

I don't know where you are but I found glow-in-the-dark powder which uses zinc sulphide from the US:

 

http://www.stevespan...uct/1586#review

 

 

Hi Swansont,

 

Ya I think I will try the straight Zinc Sulphide. I routinely use Strontium Aluminate by the trade name Super-LumiNova™. I buy that from Switzerland for $40/gram. It glows too well for my purposes with these old rolex dials.

 

thanks,

Iwc3

FWIW, if the dials used radium or tritium, as Phi alluded, the phosphor's glow wouldn't have to last long, as the material would be constantly refreshed, as it were. Tritium has a half-life of 12.3 years, so if this is an older watch, from the 60's, that means it's gone through ~4 half lives, so the tritium's activity has dropped by a factor of 16. Even if the phosphor is intact, you wouldn't get much of a glow from the tritium.

 

Whatever is used in kids playthings, like the stars you can affix to a ceiling, glow for several minutes (if they're decent ones, at least). As you noted, ZnS is a common phosphor; when you add Cu impurities, it lasts a while. Strontium aluminate is another candidate. Wikipedia says "it is about 10 times brighter and 10 times longer glowing, however about 10 times more expensive than ZnS:Cu" and that it's what's in a lot of kids' GITD toys.

 

http://en.wikipedia....ntium_aluminate

[StringJunky]

Let us know the outcome of your trials won't you?

[iwc3]

Sure will. I'm doing tests with Strontium Aluminate until the Zinc Sulfide arrives.

 

 

My problem with strontium aluminate is that I am finding my "base material" of Aluminum Oxide blocks out the glow of the strontium aluminate. I have to use more of the strontium, but when I do, the product glows way too long. I'm hoping the use of Zinc Sulfide will allow me to use the larger quantity and the glow will more approximate the short duration glow of the "old stuff".

 

This thread has been very interesting, tapping into your members chemical knowledge.

 

Iwc3

 

 

Let us know the outcome of your trials won't you?

 

 

 

[Mark E]

You can purchase the exact material to paint your watches (in many colors) here; http://www.esslinger...ous+fluorescent

[iwc3]

Thank-you Mark.

You can purchase the exact material to paint your watches (in many colors) here; http://www.esslinger...ous+fluorescent