I like sapphire for its its ability to resist scratches but I would rather have acrylic over mineral glass because you can polish scratches out and it is the most impact resistant. Acrylic also has that old school feeling. Gsm
There was one time when my Citizen Nighthawk took a hit and I thought for sure I had put a ding in the scratch resistant mineral crystal. I had just got done cutting a 3" metal pipe.. then welded a bead around the end... then filed the edges down. My Nighthawk took a direct hit by that thing and it didnt leave a mark... I had to check my watch half a dozen times to believe it. Lets just say that I have a new respect for the scratch resistant crystal that Citizen uses. Im not sure if all the crystals are created equal but the ones they use on the Nighthawks are GOOD!
There is another alternative: acrylic, aka plexiglass.
Acrylic scratches, but the scratches can be polished out. There are hardened acrylics as well that don't scratch nearly as much.
Mineral glass doesn't scratch as easily, but once it's there, it's there: you gotta replace it instead. When it breaks, it breaks in pieces.
Sapphire is artifical sapphire and is much more difficult to scratch (can be done, though!) and can even be hardened by various coatings (Sinn does this). When it breaks, it shatters into tiny pieces as it is more brittle, as you have mentioned.
What is the best? Depends.
For a high-end watch that will not see any severe use (sport, military) sapphire is appropriate because it will show the least wear over time. For a high-end military that is highly rated, sapphire can also be appropriate, under the caveat that a very thick sapphire is used to improve ruggedness.
For extreme altitudes and space flight, acrylic is the choice as it will give the most before failing, and when it fails it doesn't let tiny bits of glass/sapphire get into the equipment. Very bad when that happens. My diving watches have thick acrylic crystals as well. Remember, scratches can be polished out!
For the vast majority of lesser expensive watches, mineral glass is a very good compromise and allows the money you spend to be spent on the calibre inside the watch rather than the glass protecting the face.
A friend of mine has a Sinn 356 and was contemplating have the acrylic replaced with a sapphire crystal until he realized that he could have the acrylic one replaced a number of times before the cost came up to that of the sapphire. So once every several months, whenever he changes his toothbrush, he uses his toothbrush one last time with some nice white toothpaste to polish his acrylic crystal on his 365.
Works great, and you can't do that with glass or sapphire.
A friend of mine has a Sinn 356 and was contemplating have the acrylic replaced with a sapphire crystal until he realized that he could have the acrylic one replaced a number of times before the cost came up to that of the sapphire. So once every several months, whenever he changes his toothbrush, he uses his toothbrush one last time with some nice white toothpaste to polish his acrylic crystal on his 365.
Works great, and you can't do that with glass or sapphire.
Hey John, I always find your posts very informative and this one is no exception. Had a question: Does the "toothpaste trick" work with Seiko hardlex crystals? :thanks
my bm is going in for a new dial, and i was considering getting the crystal replaced with sapphire, as its my work watch ( firefighter)
looks like i'll be getting an acrylic.
sapphire doesnt scratch (unless a diamond) but can shatter
Mineral is good also but it scratches very easily but can be polished out.
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