WatchUSeek Watch Forums banner

1 - 19 of 19 Posts

·
Registered
Joined
·
572 Posts
Discussion Starter #1
Sapphire is just about the toughest watch crystal options today, but I keep noticing that my watch develops new scratches almost every week.
These are tiny microscratches, they arent really noticable unless you view the crystal at an angle, and in strong light. have you notticed this on your sapphire crystals??

I have a polishing cloth (the kind given to you for free at a lenscrafters) and it might have gotten a little dirty, I had some pennys in the same place where I kept the rag, and I was using this to polish smudges off the crystal (most likely the source of all these tiny scratches)

Is Sapphire supposed to resist these types of scratches?

Also for bonus points does anybody know if the orient CFT00004b has the antireflective coating on the outside or inside of the crystal? (I think I heard somewhere that its applied to the inside of the crystal but so far I havent been able to confirm or even find that reference again)
 

·
Banned
Joined
·
21,244 Posts
A Sapphire crystal is very hard, so you should not be able to scratch is as easily as you describe. The AR coat is much softer,( unless one of the hardened ones). Are you sure it does not have the AR on the outside too?
 

·
Registered
Joined
·
2,133 Posts
It is possible to scratch the sapphire crystal as well as possible to buff it out with modern abrasives, despite what my watchmaker told me. If it is the AR coating then that is also very succeptible to scratching as well as easily smudging. If you want to remove the AR I have done it with a combination of Polywatch and Toothpaste. If you want to buff out the micro scratches on the sapphire then you must invest in diamond paste and a dremel handheld rotary tool.
 

·
Registered
Joined
·
356 Posts
I have had my Omega SMP for about 8 years & every time I have seen a "scratch" on the crystal, it wipes off with a cloth.:-! I have examined it under magnification & it is clean. Sapphire crystals are very high on my list of good things. IMO A watch can't look new with scratches on the crystal. I though that this one had AR on both sides, but maybe it's only on the inside, unless it is very, very hard, as I am rough on watches. Most of my mineral crystal watches have scratches on the crystal.
Cheers,
kev
 

·
Registered
Joined
·
126 Posts
I don't understand why watchmakers put an AR coating on top of a sapphire in the first place. Makes absolutely no sense.
 

·
Registered
Joined
·
1,922 Posts
Sapphire is just about the toughest watch crystal options today, but I keep noticing that my watch develops new scratches almost every week.
These are tiny microscratches, they arent really noticable unless you view the crystal at an angle, and in strong light. have you notticed this on your sapphire crystals?
No, haven't noticed that on any of my watches with sapphire crystals. While sapphire can be scratched, just wiping it with a cloth really shouldn't be scratching your watch.

Like others have suggested, it may be an outer AR coating that you're scratching. Usually the AR coating is on the bottom/dial side of the crystal, but there are some watches that have both sides coated. It works very, very well, but the coating certainly can be scratches.

However, is it also possible that your watch has a mineral glass crystal and not a sapphire crystal? Which watch do you have?
 

·
Moderator Public Forum
Joined
·
22,082 Posts
Sapphire is just about the toughest watch crystal options today, but I keep noticing that my watch develops new scratches almost every week.
These are tiny microscratches, they arent really noticable unless you view the crystal at an angle, and in strong light. have you notticed this on your sapphire crystals??

I have a polishing cloth (the kind given to you for free at a lenscrafters) and it might have gotten a little dirty, I had some pennys in the same place where I kept the rag, and I was using this to polish smudges off the crystal (most likely the source of all these tiny scratches)

Is Sapphire supposed to resist these types of scratches?

Also for bonus points does anybody know if the orient CFT00004b has the antireflective coating on the outside or inside of the crystal? (I think I heard somewhere that its applied to the inside of the crystal but so far I havent been able to confirm or even find that reference again)
Does the watch crystal have anti-reflective coating applied on the outside? If so that material is relatively soft and easily scratched if the watch is simply stored in a drawer or box with other stuff.

There are unfortunately more than a few watchmakers who push the look of their fully coated sapphire crystals but fail to warn owners about the downside.
 

·
Registered
Joined
·
663 Posts
Thanks for the post.
I was wondering - how really hard is AR coating on sapphire? And does it tolerate everyday wipe with tissue?
Well, I guess it depends on the watch, but I clean the crystal (I use a lens cloth, not a tissue) on my Sinn U1 whenever I wear it (it gets wrist time quite often) and I do not notice any difference from when it was new (I've had the watch 8 months).
 

·
Registered
Joined
·
263 Posts
Also for bonus points does anybody know if the orient CFT00004b has the antireflective coating on the outside or inside of the crystal? (I think I heard somewhere that its applied to the inside of the crystal but so far I havent been able to confirm or even find that reference again)
If you can see that characteristic bluish purple AR reflection all the way to the very edge of the crystal, then it's likely that there is an outer edge coating

i clean my Damasko incessantly, often with just my shirt sleeves, it's been 3-4 months and i haven't seen a scratch of any size yet
 

·
Registered
Joined
·
351 Posts
I don't understand why watchmakers put an AR coating on top of a sapphire in the first place. Makes absolutely no sense.
I love watches with 2 sided AR coating. The double AR makes the dial look so clear that it seems like there is no crystal at all. That said, I would never want this on a watch that you would abuse as the outer coating can scratch. I've owned 4-5 watches this way and only one became scratched.
 

·
Registered
Joined
·
9,327 Posts
The bluish reflection can also be the result of an inner AR coating as well. For what its worth, I have never scratched a sapphire crystal but have scratched an AR coating. Outside AR coatings pick up smudges and fingerprints like crazy, and I much prefer an inner coating, which is almost as good at producing a very clear and optically transparent crystal.
 

·
Registered
Joined
·
1,684 Posts
Well, I guess it depends on the watch, but I clean the crystal (I use a lens cloth, not a tissue) on my Sinn U1 whenever I wear it (it gets wrist time quite often) and I do not notice any difference from when it was new (I've had the watch 8 months).
If you can see that characteristic bluish purple AR reflection all the way to the very edge of the crystal, then it's likely that there is an outer edge coating

i clean my Damasko incessantly, often with just my shirt sleeves, it's been 3-4 months and i haven't seen a scratch of any size yet
Right. I do the same on my Breitling since December, 08 when I've bought it. Just curious how durable AR coating can be. Not a once I saw TV collectors wipe Rollexes, APs, Pateks just against their jeans or sleeves
 

·
Banned
Joined
·
21,244 Posts
Very true, Sinn also uses a hardened AR coat.
I do not know if the actual bond between the crystal and AR coat is very strong.
I suspect not, that is why some forumers have experienced that even those coatings can be scratches, and removed fairly easily.

The longest I have been cleaning an AR coated crystal is 3 years, and I usually clean it with my T-shirt. But I always blow away loose dust and particles first.
No scratches as of yet. (Sinn U2)

The bond is incredibly important. As a dentist, that is one of the problems with ceramic or composite plastic restorations:
The restoration is very strong, the tooth is strong, but the bond between those is much weaker.
 

·
Registered
Joined
·
7,751 Posts
Chain mail armor is only as strong as its weakest link (and Milanese bracelets too! :-d) ;-)

Same problem with composites (laminated composites) ... the resin used usually is the probable cause of failure (de-lamination).
 

·
Registered
Joined
·
572 Posts
Discussion Starter #17
No, haven't noticed that on any of my watches with sapphire crystals. While sapphire can be scratched, just wiping it with a cloth really shouldn't be scratching your watch.

Like others have suggested, it may be an outer AR coating that you're scratching. Usually the AR coating is on the bottom/dial side of the crystal, but there are some watches that have both sides coated. It works very, very well, but the coating certainly can be scratches.

However, is it also possible that your watch has a mineral glass crystal and not a sapphire crystal? Which watch do you have?
HilltopMichael: I have an Orient cft00004b ...the one in my avatar pic..The orient website describes the watch as having sappire crystal and antireflective coating...no indication however if it is applied to the outside. But I dont think so.

To everybody who has replied thank you for your input.
 

·
Banned
Joined
·
5,850 Posts
HilltopMichael: I have an Orient cft00004b ...the one in my avatar pic..The orient website describes the watch as having sappire crystal and antireflective coating...no indication however if it is applied to the outside. But I dont think so.

To everybody who has replied thank you for your input.

I could be wrong, but I don't think Orient uses any external coatings.

I recall some guys commenting that their wife's diamond ring would cause a scratch on their sapphire, especially if both were worn while sleeping.
 

·
Banned
Joined
·
21,244 Posts
Chain mail armor is only as strong as its weakest link (and Milanese bracelets too! :-d) ;-)

Same problem with composites (laminated composites) ... the resin used usually is the probable cause of failure (de-lamination).
Exactly! I would love to know what kind of bond there is between the 2 materials (AR coat & Corund crystal).
My (somewhat limited) chemical knowledge tells me it is in fact a quite weak bond.
That is the reason quite a few WUS members have bee able to remove the AR layer.

If I explain like this:
The situation on an AR coated crystal is similar to what you have if you paintpolished sheet steel with a very hard, enamel like paint. Once you put enough lateral (side) pressure on the paint, it will start slipping, tears and flakes off the metal surface.

In dental composites, the Plastic Matrix contains a very large % of Filler particles, made from certain glasses, silicates or ceramics. Those particles are extremely small, around 0.5 um
Upon loading the matrix cracks, but the cracks stop very soon, when they hit a filler particle.
The usual reason for replacement of those fillings has to do with the failure of the bond between the filling and the tooth, not because the actual filling fractured.
Sorry to be a bit Off Topic!
 
1 - 19 of 19 Posts
Top