# Can someone explain what a 'double domed' sapphire means?



## dave_in_gva

Hi all....it's my week for questions :-d

I've seen that MKII watches all have 'double domed' sapphire crystals.

I assume this means both surfaces are convex but more importantly can anyone tell me why this might be an advantage? If I had to guess I would say it probably increases the ability of the watch to withstand pressure or a blow to the crystal. Maybe it also magnifies the dial face somewhat and makes the dial more legible....dunno.

Either way, I haven't come across other watches that have double domed crystals, so thanks if people can enlighten me to what its all about.

Dave M


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## Dave E

Yep, it means convexed on both faces, rather than flat underside and curved top.

Advantages? Less optical distortion of the dial, and I think it will be stronger.


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## caesarmascetti

The arch on both sides makes it better able to disipate the forces of impact so yes it is stronger, and once treated with an inner A/R coating it looks almost like a quality lens the dial really "pops" sharp and clear. I own a Stingray witht he A/R it's beautiful. Just for the sake of conversation I also own and O7 LM6gmt which is at the other end. It too has a domed crystal and the dial looks fuzzy because it has no A/R coating it is also unreadable in direct sunlight due to distortion (no such problem witht he Stingray) I've sent the O7 to Jack at IWW for an A/R coating among other things.


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## dave_in_gva

Thanks Caesar....very clear and helpful.


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## VoiceOfSticks

Helpful - thanks!


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## tpd80

I know this is a dead thread but i thought i would add my 2 cents. A friend has a single domed sapphire on another brand and its horrible to look at.

when you look straight at it, 90 degrees to the dial, everything is fine. When you look on an angle, on his watch, of about 45 - 0 degrees you cant make out anything because the dial is so distorted by the curving of light.

my double domed i can look at the dial and its visually perfect from 90 to almost 180 degrees.


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## JDS (Ohio)

Dave E said:


> Yep, it means convexed on both faces, rather than flat underside and curved top.
> 
> Advantages? Less optical distortion of the dial, and I think it will be stronger.


Convex on *BOTH* sides? I thought "double domed" meant it was convex on the top (outer) side, and concave on the bottom (dial/inner) side. :think:


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## rmasso

JDS (Ohio) said:


> Convex on *BOTH* sides? I thought "double domed" meant it was convex on the top (outer) side, and concave on the bottom (dial/inner) side. :think:


You are correct, convex on outer, concave on inner.
Rich


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## Sean779

rmasso said:


> You are correct, convex on outer, concave on inner.
> Rich


something like this, right? * )) * (can't have concave without convex, in this case anyhow.)


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## rmasso

Sean779 said:


> something like this, right? * )) * (can't have concave without convex, in this case anyhow.)


Correct. 
Rich


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