There no known way to repair a sapphire crystal. It would not be difficult to replace it. A new crystal is about $25-$45 plus labor. You can save a few dollars by getting a replacement mineral crystal (can be scratched more easily). If there's no watchmaker in town with in-house ability to do this, there are many who routinely do this for Seiko owners (search online). The ad on top of the page "Watch Central" would likely be able to do this procedure for you.

 

If you have the piece and it's a really good fit (so no small bits broken off it) you might get a reasonable result gluing it back in using UV setting resin (the same stuff they use to fill windscreen cracks). It won't be perfect because the refractive index of the resins tend to be matched to normal glass but, done carefully, it could well be an improvement on how it is now.

 

Thanks for the advice; I know I’ll eventually have to buy a new one, but right now I don’t have the funds for that. The UV resin sounds like a good idea in the meantime... is it sold at Hobby Lobby or automotive stores?

 

Automotive stores....something like this. I've not done a watch crystal repair with it but have done windshield "stars" or other rock damages with it. Hit or miss. I feel your repair will be close to better than it is now.

The stuff weeps or wicks into a windshield star and causes it to "disappear" almost. Or, it fixes it and still shows some.

https://www.autozone.com/sealants-g...s-adhesives-and-tape/windshield-repair/3m-8580-windshield-repair-kit/249378_0_0

 

StephenReenII...Hello.

I will suggest that your chances of 'repairing' this damage are slim...very slim!

Instead of investing several dollars in UV glue, why not start a Fund for a new crystal? If this were my Bulova, I'd probably install an old-fashioned plastic crystal...they last for years / do not change color / may be repaired @ scratches & light chips...unlike these glass-like creations, that look Great, until they're damaged.

I have owned and worked on watches just like this, and think the World of plastic crystals...they are not expensive / they look good / they can be polished!

And: you're pretty lucky here: a damaged crystal is one thing; a slightly different application of whatever force chipped the crystal, & your case would look bad, too...!

Michael.

 

That's a bad hit. I say you replace the crystal yourself. It can be done. I've done it many times. https://blog.esslinger.com/how-to-replace-a-watch-crystal/ It's a very good thing to be able to do for yourself. Order a new round sapphire, get a few basic tools & giddyap.

 

Hard to tell from the photos and don't know the model, but is it not a slightly profiled crystal on these?

If it is then anything but an original is going to change the appearance (which the OP may or may not mind) and - at least here in the UK - Bulova won't supply parts, so getting an original would mean returning it to them which would almost certainly involve a full service charge following an impact like that.

Hence the suggestion of trying UV resin. The RI of sapphire is higher than any currently available (although Mitsubishi Gas Chemical are currently developing one in their LumipluS range specifically matched for sapphire) so it won't be invisible but - with a thin enough application and enough care to exclude bubbles - I'd bet on it being a lot better than people expect.

 

The UV adhesive works on car windows because the crack is very narrow, on the range of microinches, and there's no contamination in the crack because nothing can get in there (hopefully) before you glue the crack up. When you chip a crystal, you create powder at the point of impact that must be completely removed (any stuck in the gasket?) before you can get a fit-up that's even close to the car window crack.

Index of refraction doesn't affect the light path so much as create a reflective surface due to the differences in indexes of the materials, think AR coating or oil on water. You don't notice it in a car window because (usually) the crack is parallel to your line of sight, not so with your crystal. Also, as best as you try, I doubt the loose chip will fit up anywhere close to how a window crack fits.

That being said, if you can't afford a new crystal, the adhesive is the only choice and it can create a very optically clean repair. I've repaired several car windows with it in the past 20 or so years. My only failure was a star on the wife's Lexus; I couldn't get it to penetrate into the longer cracks to save my life. I tried a little heat and turned a one inch star into a galaxy! The replacement is still at the dealer awaiting my first loose $1000.

Good luck

 

The issue with the refractive index here is that the light will change direction (twice) as it passes from the sapphire to the resin to the sapphire. It'll bend off it's original path at the first interface, travel the thickness of the resin, then bend back to its original direction at the second onterface. That will slightly offset the image of anything viewed through the repair. The bigger the RI mismatch, and the thicker the resin, the greater that effect will be.

The same thing happens between the sapphire and air, which is what's causing the distortion of the figures behind the chip. Because of the varying thickness of the broken bit different parts of the image get shifted different amounts and distortion happens.

Replacing the chip would greatly reduce that by restoring the total path length through the sapphire and leave a (relatively) even offset depending on the thickness of the resin.

 

I guess the thing I left out is that the crack needs to be like the crack on a car windshield, microinches in thickness, then you don't get any distortion due to index of refraction issues. I've been amazed how well it works on cracked car windshields, now you see it, now you don't.

That being said, the goal is probably impossible since the chip has separated from the base. All of my argument is based on having the intact chip to place back in the hole and fitting it such that the crack is microinches in thickness.

Trying to fill the hole with adhesive is a waste of time. Perhaps if there was an adhesive that exactly matched the sapphire, it would work but I seriously doubt it would be invisible (like my car windows were).

 

Agreed, it won't be invisible but - as long as it's done with care - the physics pretty well guarantee it'll be better than it is

 

Dunno what makes more sense to you, but I'd sure rather buy a new crystal for $20 than a pack of glue for $17.

 

But it won't be a "$20 crystal" for that, especially if your'e going to keep the original profile , thickness and deep bevelled edge!

 

Thank you so much, everyone! Eventually, I am going to replace the current crystal with another sapphire one, but right now I don’t want to spend any more than I have to... funds are tight for the next week. However, I achieved a great result with the window resin (Picture 1). Unfortunately, it later dried out, and now doesn’t look nearly as good (Picture 2). Regardless, I think I might be able to delicately pry the chip out and refill it with resin... anyway, if I can get it back to Picture 1 quality, I’d be more than happy. Thank you again, everyone!

 

Thank you so much, everyone! Eventually, I am going to replace the current crystal with another sapphire one, but right now I don't want to spend any more than I have to... funds are tight for the next week. However, I achieved a great result with the window resin (Picture 1). Unfortunately, it later dried out, and now doesn't look nearly as good (Picture 2). Regardless, I think I might be able to delicately pry the chip out and refill it with resin... anyway, if I can get it back to Picture 1 quality, I'd be more than happy. Thank you again, everyone!

That looks like you may have had some air or moisture trapped. If you can remove it intact then use a little more resin and sort-of "float" the chip down into place. Within reason you can take your time making sure there's no bubbles as long as you're not working under bright sunlight or another UV source. Then, as ExpiredWatchdog suggests, secure it so it stays in place and put it in direct sunlight to set. A layer of clear tape starting on the case back, over the chip, and back round to the caseback should hold it securely enough.

Once it's set you can remove any excess quite easily with a razor blade.

Your "first photo" result should be easily obtainable once it's dry with a little care - bear in mind, many date magnifiers are applied with this stuff and remain secure and clear for the life of the crystal!

 

I wouldn't risk gluing the crystal to the case.

 

Did you have the chip clamped in place? If not, I suspect the adhesive swelled as it crosslinked and widened the gap. Nice try anyway.