Happy to have my armchair kicked over, anytime

I obviously don’t understand all of your post’s explanation, but as for the summary item copied above I think get the gist.

The first item: as between different sapphire crystal models, this would come into effect only if the crystals themselves were of differing qualities or finish, and I suppose this is the sort of deep engineering we’ll never back into by reason alone; but as between sapphire and plexi, I assume the former tends to have a higher index of refraction and so - all else being equal - would result in more reflected light in sapphire.

The second item: the bold point appears to assume there is frosting of a surface, and that the more frosted height the more reflected light - but I wonder, is this only true of the surface is frosted? If so, I assume it’s because only the frosting would change the light direction (assuming full absorption on the other side of the crystal).

The third item: this item effectively gets at the item I’ve focused on above the most, which is the degree of slope to the crystal.

If that’s roughly all correct (is it?), then in equally rough summary: assuming sapphire of equal quality/index of refraction, the “milky ring” we would expect to be most observed when

(A) there is a lower radius of curvature at the edge of the crystal (e.g. more steeply domed at the edge, such as we know to be the case between the 1861 and 321)

(B) a surface on the crystal is modified to have a higher index of refraction, such as possible frosting/roughing of the surface, with greater frosting or greater surface area of frosting increasing the effect (e.g., which we don’t know whether is utilized at all, or differently, as between the 1861 and 321 - but would like to know)

(C) the surface of the crystal is in greater contact (by surface area) with a less light absorbent material (e.g., a white rather than black gasket)

 

I noticed the platinum 321 (also sapphire) appears to lack the milky ring (at least in Omega’s stock photos/renderings)



If so, that’s a 42mm case/sapphire that may also have a sapphire design different from its 42mm counterpart speedys.

And if so, might the use of this different/milk-less crystal might begin to look like a sometimes “premium” offering?

This had me looking through other “premium” or limited edition sapphire watches, and I found Omega stock photos lacking the milky ring, with product sheets listing the “Domed scratch-resistant sapphire crystal with anti- reflective treatment on both sides.” I looked at the Apollo 11 50th (SS and Moonshine), DSOM Alinghi, and a few others: stock photos showed little to no milk, product sheet list a “domed” sapphire.

I wondered for a moment if perhaps Omega’s stock photos could be specially “enhanced” to reduce the appearance of the milky ring (or merely renderings). But, the FOIS product sheet lacked the “domed” mention, and compare the stock photo above to the stock photo of the FOIS:



If a rendering or enhanced, they stayed true to the milky ring - and its product sheet has no mention of “domed.” Am I forgetting the FOIS to have a polished rehaut or something, explaining this away?

So then I wondered about the new sapphire 3861, since it’s now included on the Omega site.

Well, low-and-behold, the product sheet reads “Domed,” and the stock photo appears somewhat milk-less:



But this stock photo/rendering does not square with other IRL photos, such as the comparison photos listed above. IRl there appears to be far more milky ring.

In all, I think Omega’s website product sheets are likely imprecise, and not a reliable piece of intel. Perhaps even more suspect are the stock photos/renderings. And as Al’s technical product descriptions showed, there’s an entirely different nomenclature available out there to further confuse the matter of which watches have which type of sapphire.

I’ll be interested to get a profile picture of the new 3861 to compare it with the .321 profile.

 

I think you got what I am trying to say; except for B) above; the index of refraction is an intrinsic material property. You pick your glass or plastic or sapphire, you got your index of refraction. You can't change it.(*) The degree (roughness) of frosting, or the area of frosting, are different, external properties of the part.

Obviously, this is all just my guess; physics, schmysics. What we need at this point is somebody willing to pop out the crystal from their watch and take a few pictures for the greater good of watch science. Or have their kids pop it out by accident, and send it to Archer for getting fixed, and Archer takes some pics. Or somebody with a stash of Omega crystals chiming in.

(*): Not strictly true; you can by making optical metamaterials; look up 'optical cloaking'. But I don't think watch manufacturers are there yet ;-)

 

I think the amount of milky ring you see for the same watch depends on and varies with a) the viewing angle and b) the amount of light falling on the watch from mostly the side and illuminating the frosted area. The light needs to get into the crystal, bounce around inside until it hits the frosted area, change direction there (due to the frosting), and then exit through the strongly curved (small radius) edge of the crystal towards you.

Like, when I position my Speedmaster coaxial with the dial perpendicular to a computer screen, looking at the watch straight on parallel to the screen, and then shield the watch from the screen with my other hand, I can change the appearance of the milky ring a lot.

 

Photo credit to RJ & the Fratello team, taken from here: https://www.fratellowatches.com/this-week-in-watches-january-9-2021-happy-new-year/

This milk is so thick that it's conjuring up the taste of string cheese in my mouth.

 

It all boils down to that clearly Omega is not paying their engineers enough. Or not paying the right engineers.

 

This is consistent with what I’ve seen in various pictures, and a video: so I would guess it has a sapphire similar in form to the 1861 sapphire.

If instead it has a sapphire similar in form to the cal.321, I’ll just shut down this thread and go look at threads about end links

 

I see what I did there; index of refraction is intrinsic to the material, whereas I intended to be speaking instead of, essentially, the amount of total light refracted as a result of passing through the sum total of the physical alterations of the material

all good - we’re on same page, I had just misused my physics schmysics terminology

Anywho...

 

I experimented a bit with a laser pointer: it's easy to see how the light gets trapped in the outer circumference ring of the crystal, bouncing around inside and illuminating the frosted surface pretty evenly.
In the first pic the laser beam is parallel to the dial, and just touches the crystal near 12 o'clock from the outside. The whole milky ring illuminates green:



In the second pic the laser hits the crystal again near 12 o'clock, but this time with the beam direction perpendicular (normal) to the dial. Same effect, which demonstrates that the initial light direction does not matter much. As long as a part of the frosted circumference of the crystal is illuminated, it reflects the light diffusely in all directions, and a large part of the bounced off light is trapped inside the cylindrical part of the crystal, more or less illuminating the whole milky ring.



Sapphire traps about 30% more of that diffusely reflected light (larger index of refraction), so all else being equal a sapphire crystal of the same shape and surface treatment will show a brighter ring than a glass crystal. I'm guessing it's also easier to flame polish (or just polish) glass than sapphire, so maybe glass crystals do not have this frosty surface to begin with? Although, I think Archer was saying the frosting might serve a purpose for sealing.

I also put the 18mm (=wider version) Komfit back onto the Speedmaster.

 

Great idea; I’d love to have a handful of watches we’ve discussed with different crystals under a same conditions

 

Your chronometer marker is not centered. Like REALLY not centered.

 

I agree, that particular image does have quite a froth to it.

I wonder what lighting situation makes it most visible. And, what components in the sapphire would make it less noticeable. On my CoAxial, the milky ring isn't as noticeable, though I would imagine the glass composition would be the same. . . .

 

Could also be the composition of said sapphire, and the refractive effect of that curvature at the edge. Perhaps I am saying the same thing, but we experience this in glassware, automotive glass etc, more important as a refractive distortion in automotive glass. More quartz yields a different distortion than, say, additional silicon or polymers would. It's like looking the the edge of an orange drafting triangle in shallow light - it will show light coming through the thickness of the material and illuminate in some light. Less evident in perpendicularly lit situations.

Sapphire glass is defined as Al2O3, and appears to be singularly pure, so I assume the geometry of the edge is the variable here.

I'm hesitant to compare Omega's stock images - as listed on their website. Though they show detail for illustration purposes, the effects of crystal refraction can be PhotoShopped out, or lit with studio lighting to dramatize (or reduce) reflection, refraction and other detail.

 

It’s true that it is not centered.

After running a few tests (nothing’s magnetized, no creep, always resets to same position, etc.), the hand is simply not aligned correctlyz That means my “single watchmaker” did a sloppy job of installing the hand to 0, to the degree of 1/5th a second position (the bare minimum it could be misaligned, really).

That the hand is misaligned by even 1/5 a second is irksome no doubt; and were it not COVID times I’d be tempted to do something about it sooner.

But the reality is, I can’t see that 1/5th second with my eyesight, and I’m not timing a reentry burn anytime soon. So, I’ll likely just try and remember to have it reset at its first service.

 

Pretty sure this was me as I was debating trading my sapphire sandwich for a hesalite unless I found a way to eliminate the milky ring. Archer was nice enough to humour me as we dug into this.

Funny enough as a result of that research a couple of years back I was able to track down someone selling a sapphire crystal and got them to send me pics of it unmounted.

Not sure these are helpful or not but here they are...

 

@Jakemeister1000 was kind enough to take a profile photo of the new 3861 sapphire speedy (top pic):





if there’s a difference with the cal.321 (middle pic), It would seem to need calipers to notice - they look too similar to explain away the perceived differences in milky ring.

And so both seem equally different from the prior model’s sapphire (bottom pic)

 

Thanks, Lex! it's tough though to make out how rough the outwards facing cylindrical surface that is invisible when mounted (disappears inside the bezel) actually is.
I assume (question for Archer) only the flat bottom surface touches the gasket, or does the gasket wrap around the side of the crystal, and touch the cylindrical surface?
To me it seems both the bottom surface and the hidden part of the outside cylindrical surface are unpolished, but I find it really hard to tell. For example, looking at the reflections from the left side of the crystal in the last picture it seems the edges of the flat bottom surface are beveled, and appear polished; below that reflecting edge seems to be an unpolished band, and then further down there is again reflection from the higher (lower in the pic) part of the outside cylindrical surface.

 

Only on the OD of the crystal, not under it.

 

Having now seen the profile of the new 3861 crystal, and that it appears to be very close to the cal.321 in profile, I'm stuck wondering what else may cause a difference in degree of perceived milky ring between the two watches (including given that @Archer has confirmed they both use the same, black, gasket).

In truth I've not held the 3861 in hand to compare side-by-side; and in fairness owners of the 3861 are saying the milky ring is less pronounced.

But at the same time, I've now tried and failed to capture a picture of the cal.321 with anywhere near this much milk:



If folks with 3861 say there is less milk than the 1861, I'd guess it is the result of the difference in crystal shape and the resulting changes to refraction, etc., being discussed here - together perhaps with the change from grey to black gasket.

But, something more and else appears to be going on to fully explain the cal.321's lack of milk compared to the 3861.

 

We're rooting for ya to solve this milky mystery one day. The truth is out there.

Too bad this fella only wore his Speedmaster for this single episode. A little more time spent with the watch, and who knows... maybe he'd have been inspired to chase after this unexplained phenomenon with same fervor he had for hunting lake monsters and UFO's.



Keep up the great work, and don't get discouraged!




Photo credit: foxmulder's wrist watch blog....