Cool info and thanks. I’ve seen the green Lumibrite and C3 behave similarly under artificial and direct sunlight. Same goes for the blue Lumibrite and BGW9.

Are you building a watch based on lume or what’s driving this inquiry?

 

: ) That's kind of you.

It's really just curiosity. For analog watches, as it ended up, I only own BGW9 these days. I've wanted to compare to other lumes, but found lots of folklore online with not too much else. As you say, it would make sense that the green and blue Lumibrite would resemble C3 and BGW9, respectively. It is a challenge to estimate how much is tech and how much is marketing, but I know it isn't completely a commodified yet-- glow in the dark has come a long way since I was a kid!

I have thought building my own watch and painting the lume myself, but as of yet, never done it.

 

I always thought that Lumibrite was just Seiko's proprietary name for C3.

 

I'd believe that. In that case, I wonder if the C3 vs. BGW9 initial brightness vs. longevity folklore that I (and apparently GPT-4) heard is real.

 

• C3 – A faint yellow hint in daylight with a strong green glow at night. If we take that as 100% light then the others can be compared.
• BGW9 – White in the day and blue at night. 95% of the strength of C3
• C5 – Green/yellow in both conditions but reduced to 89% of C3
• The compounds then reduce in order through C7, C9, and many more right down to:
• C1 – White with just 31% of C3, and the weakest called Dark Red which has just 22% of the strength of C3.

About Swiss Super-LumiNova® Luminous Pigments

Meigeer Watch uses Swiss Super-LumiNova® Luminous Pigments for their high end quality watches

www.meigeerwatch.com

https://www.keepthetime.com/blog/super-luminova/

my C3 watches are the best IMO.

you also have to remember that is not only the paint, but the size and depth of the lume dot. I tiny dot on a chronograph of c3 won't be as bright as a huge round deep dot of c3 on a divers watch.

 

C3 lasts all night…

…as does the BGW9.

Whatever Citizen uses on their divers works well, too.

 

I know what you mean, all of them can look great and last long. I'm still curious if the luminosity vs. time curve of different lumes (with volume of application controlled) is different as I've anecdotally heard.

 

Two factors in watch lume;

The formulation, lume powder, pigment, fillers, binders. Strontium Aluminate is the chemical that glows, adding the other bits creates the various shades/colors.
More Strontium = more glow, more pigments & binders = less glow.

The other factor is the amount of lume applied. 1-2 layers = weak lume, more layers = greater glow.

 

I know what you mean. My impression is the same, that for example the red variant is basically C3 with impurities that make it red.

Even so, I thought that the blue vs. green distinction for e.g., C3 and BGW9 might be more fundamental and less of an afterthought. I read this on https://en.wikipedia.org/wiki/Strontium_aluminate (emphasis mine):

Strontium aluminate phosphors produce green and aqua hues, where green gives the highest brightness and aqua the longest glow time. Different aluminates can be used as the host matrix. This influences the wavelength of emission of the europium ion, by its covalent interaction with surrounding oxygens, and crystal field splitting of the 5d orbital energy levels.[2]

The excitation wavelengths for strontium aluminate range from 200 to 450 nm, and the emission wavelengths range from 420 to 520 nm. The wavelength for its green formulation is 520 nm, its aqua, or blue-green, version emits at 505 nm, and its blue emits at 490 nm. Strontium aluminate can be formulated to phosphoresce at longer (yellow to red) wavelengths as well, though such emission is often dimmer than that of more common phosphorescence at shorter wavelengths.

For europium-dysprosium doped aluminates, the peak emission wavelengths are 520 nm for SrAl2O4, 480 nm for SrAl4O7, and 400 nm for SrAl12O19.[3]

Eu2+,Dy3+:SrAl2O4 is important as a persistently luminescent phosphor for industrial applications. It can be produced by molten salt assisted process at 900 °C.[4]

The most described type is the stoichiometric green-emitting (approx. 530 nm) Eu2+:SrAl2O4. Eu2+,Dy3+,B:SrAl2O4 shows significantly longer afterglow than the europium-only doped material. The Eu2+ dopant shows high afterglow, while Eu3+ has almost none.

The article doesn't specify a detailed molecule for the strontium aluminate with blue-green or blue emission, only for the 530nm green emission. I've looked into a few of the references on Google scholar. There's a lot to take in, but I haven't found anything yet that confirms the blue/aqua glow is more enduring than green.

 

I like to check my watch when I get up for a wee in the night and BGW9 is usually best for this.

 

Maybe you found out what the W in BGW9 stands for!

Same experience, but I wish there were a scientific experiment to reinforce this.

 

 

I don't quite like the theoretical bit but am subscribing in case anyone wishes to do another real-world test. I've done it twice (and reported the results on this forum), and will be interesting to see another real-world comparison.

 

Both C3 and Lumbrite stay bright through the night in my experience and are very easy to read in the morning.

 

Does anyone have two versions of the same watch in BGW9 and C3? If so, it would be really cool to do an apples-to-apples comparison of initial brightness and brightness after 20 minutes or an hour. I'd expect the Scurfa BGW9 and C3 are similar enough in application; however, the C3 models are rare, and I don't have one to do it.

 

I'm considering this watch which uses C3 on the dial. You can see from the picture what it looks like during the day and what it looks like at night but what I'm concerned with is what it will look like in dim light. Is it going to have a faint green glow or remain like the top photo?

Photo from deployant.com