I've been wearing my PO 8500 daily for almost a year now, including on a few shooting trips. I just noticed this morning that there's a tiny scratch in the sapphire crystal over the dial. It's tough to see unless I really look for it, but knowing where it is, my eye goes straight to it on close inspection. Is there anything short of replacing the crystal that can be done about this?

 

Sorry to hear that. leave it till next service Omega will sort it out. It is possible to scratch sapphire, one member on a thread the other day was certain it was impossible to scratch.

 

Could you show us a picture of the scratch?

 

It is most certainly possible to do. I've done it to my Breitling Steelfish...and the same way, while at my work bench in the basement working on something.

I've been trying to catch a picture of it, but because of it being relatively small and me not having a proper camera (thank you iPhone), I can't really get it to show up in a picture. The best description however, is that it looks like a smear on the crystal, but wiping it clean with a damp microfiber cloth followed by a dry one doesn't get rid of it.

 

Don't worry sounds minor. At next service they will replace crystal.

 

The scratch you see is more than likely just a scratch to the outer Anti Reflective coating that comes on the PO 8500 crystals. If it was a deep and very noticeable scratch it would most likely be a scratch through the coating and all the way down to the sapphire, but the way you describe it sounds much more like the first option.
As such, you have three different options for dealing with the situation
1 - Fully remove the AR coating. A lot of people have done this, and it either takes a decent amount of elbow grease with a cloth and mild polishing compound and/or a trip to a qualified watchmaker. Removing the AR coating will get rid of the surface scratch but not affect the rest of the crystal. Obviously some reflections will now be noticeable whereas before the crystal looked perfectly transparent, but you won't need to worry about picking up any more scratches unless your daily routine involves punching diamonds.
2 - Remove and then reapply the AR coating. I'm not sure how feasible this is but I though I remembered seeing that it's possible. More painstaking but most likely a less costly option than replacing the entire crystal.
3 - Replace whole crystal.

Best of luck with the situation, and hope it can be resolved soon.

 

The hardness of any genuine or synthetic mineral is calculated based on its resistance to be scratched by another mineral of its kind. The MOHs scale has sapphire (corundum) at a hardness of 9, and diamond at a hardness of 10. This might imply that sapphire is almost as hard as diamond. Not so! Depending on which expert you read, diamond is about 100 times more resistant to being scratched by a diamond, than sapphire is to being scratched by another sapphire! I believe the AR coating on these crystals is oxide of fluorine. Whether it is the coating or the crystal that is scratched, it is a nuisance!

 

I'm not sure that omega will replace it as part of service. They may replace it at service time, for a cost. I believe the crystals go for about $650 USD.

Can you learn to live with it?

 

I was sure they would charge for the crystal when the watch was serviced as an additional cost. However, $650 USD my god are they that much! No point if it is not noticable. @Archer will know the exact cost I am sure. That crystal costs £438 sterling pounds, can't be right??

 

Not knowing the reference makes it harder, but yes, looks cheaper than I recalled.. ofrei has some for 168.16xx for $228

http://www.ofrei.com/page_168.html

 

Crystals vary quite widely in price. Few are less than $200 though for sapphire.

 

That makes more sense in sterling that is £153, still a tad high but in the right ballpark.

 

Thanks for reply AL. I was wondering on a tangent how much is the moonwarch crystal for a modern version? Must be a lot cheaper for obvious reasons?

 

Acrylic is cheap so $40 or so. Sapphire will cause some pain if you need a new one...

 

Kind of boggles the mind that people put AR coatings on the outside of vulnerable crystals. Inside coatings turn the crystal invisible enough for me, though I admit I haven't done a side-by-side comparison.

 

Heres an Aquaracer and its very scratched

 

From what you describe, it sounds like it is definitely a scratch in the AR coating as it doesn't catch my fingernail, it's just visible in just the right light from the right angle. I'll wait until service time rolls around and then see what the recommendation is.

 

The reason for the coating on the outside makes some sense. As light reaches a reflecting surface, some of the light penetrates the surface, but light outside the "critical angle" is reflected away, and doesn't penetrate. With the coating on the inside of the crystal, the reason for applying it is defeated! The un coated outer surface loses just as much light as if the coating wasn't there at all! I don't know in percentage terms how much the coating on the top surface improves the light absorption, but it is considerable!

 

I think what @wsfarrell meant was why have a sapphire crystal, which is known for its hardness and scratch resistance, if you then coat it with a material that's neither hard nor scratch resistant. Yes, the AR will make the crystal dissapear and the dial more legible, but at what cost?
Cool old post here that goes into watch AR coatings. Basically, the internal only AR coatings on Bretilings at that time made reflectance roughly 5%, while the double AR makes it roughly 1%. So 5x greater clarity, but still even with only the internal AR a very low level of light is reflected.

 

My dad has a panerai and i managed to chip the glass. I have always had faith in the scratch resistant not proof sapphire analogy. I prefer the plexiglass crystals.