[Htsthbjig]

I don't agree on most of these reasons. Light transmission is really good on sapphire, so not a great difference with glass.

I believe the number 1 reason is:

1- They want to test it first.

Apple always do tests, but most of the people do not realize it. For example, do people realize that before making the Ipad big screen they tested it in the magic touchpad?.

Between the Iphone and the Ipad there is a huge size gap that means lots of problems when you do things in the millions, so they added a glass screen to millions of laptops touchpads.

They got lots of useful information from service repairs, and they did hide their testing in front of their competitors eyes without them realizing.

Competitors used plastic in their touchpads. When they could connect the dots(it they did at all), it was too late, Apple was years ahead.

If they start selling their watches in the millions, and I think they will, mass producing sapphire will make cost plumb.

There will be testing early at a scale that nobody had done before. I worked for a company that manufactured sapphire glass for the military. We made very expensive SINGLE units for equipment like cameras, and it was only for the exterior side.

If a market is created, innovation will come. What we did was very expensive and we did not care about price.

We did work that was so "last century", like creating huge blocks like stones, then cutting and polishing it.

I am certain that a better method, more energy efficient like growing crystals in molds, is possible, but it needs to have demand in order to justify the investment.

[Shivetya]

I am going with the line in the article about the fragility of the sapphire, it simply does not take impacts as well as glass especially in the sizes being used. Kind of like how yields are with semiconductors, getting this large requires much better processes than they have now.

I am simply glad we got past the use of glass on the backs of phones like the iPhone 4 generation had. All that did for me is have me learn how to swap the piece myself.

I think glass breakage is pretty low in the issues people have with these phones, weight and battery life are bigger issues.

[JunkDNA]

Apple has been testing sapphire. It has been in the cover for the camera since the iPhone 5 over two years ago. What is interesting is that they have gone back to glass for the lens cover in the new phones. My wife had a problem with her iPhone 5 shortly after purchase. After she dropped it on the floor (not especially hard) photos had these small, magenta flecks that no amount of cleaning could get rid of. Apple swapped it out no problem, but when I first heard that they moved back to glass for the new camera in the 6 series, I wondered if they decided that sapphire just wasn't going to work for this use case.

I suspect, they've learned quite a bit from the sapphire cover on the camera, hence their comfort in deploying it to the higher end watch models.

[CognitiveLens]

They have not gone back to glass

> Sapphire crystal lens cover [all iPhone models]

http://www.apple.com/iphone/compare/

[analog31]

Bulk transmission through the material should be similar. But sapphire has a higher refractive index than gorilla glass (1.77 vs 1.5 or thereabouts) and thus reflects more at each surface. Reducing reflectance with a coating works, but as the article points out, costs money and is less durable.

[IkmoIkmo]

Agreed. You can see this every single time. Like the fingerprint scanner, didn't go out in 4 or 5 or 6. It happened in one of their 'between' phones, in 5S/5C. They test it, if it works, okay great, now we can build our payment's product on top of it.

That's the way you can be successful. The massive risk would be to create a fingerprint thing and try to bootstrap a payments platform on day 1 when 0 users have their fingerprint scanned.

Testing is a big part of apple, and I think this screen is part of that philosophy.

[gallamine]

A quick check of Thorlabs (supplier of optics) shows that their Sapphire windows have < 90% transmission, while their Fused Sillica or BK7 windows have 90% - 95% transmission. Granted, those may be different from the current Apple glass (anyone know the exact variety) but < 90% transmission isn't all that hot.