Apple’s Steve Jobs is set to officially unveil the new iPhone later today, and one of the continuing mysteries – the advanced ceramic and glass composition of the phone’s case and face – will hopefully be put to rest.

Obviously, there is a lot of ceramic content in the electronic innards of the iPhone, but the largest amount of glass and ceramics has always been on the outside. When I first started this blog over two years ago, one of my first posts was about the ceramic content of the hard back cases of the first and second versions of the iPhone. Alas, that post and many others disappeared into WordPress oblivion during an early server swap.

But the discussion about the ceramic and glass content of iPhones was renewed back in April when the folks at Gizmodo got their hands on a prototype of the next iPhone:

“The back is entirely flat, made of either glass (more likely) or ceramic or shiny plastic in order for the cell signal to poke through. Tapping on the back makes a more hollow and higher pitched sound compared to tapping on the glass on the front/screen, but that could just be the orientation of components inside making for a different sound.”

A few days later, Gizmodo seemed to start leaning (without explanation, despite requests from me) toward saying the case is plastic:

“But why the black plastic back, instead of going with an unibody aluminum design?

[ . . . ]

The plastic back is the most obvious of the design choices. The iPad, with its all aluminum back, has seen its Wi-Fi reception radius reduced. The 3G version comes with a large patch on the top, probably big enough to provide with good reception. But the new tiny iPhone doesn’t have the luxury of space: It needs to provide as much signal as possible using a very small surface. I’m sure Jon Ive is dying to get rid of the plastic back, and go iPad-style all the way, but the wireless reception is the most important thing in a cellphone. A necessary aesthetical-functional trade-off.”

I think Gizmodo is off the mark here. More than once last year, experts in multifunctional ceramics reported to me they were being hounded by Apple engineers to discuss their work. Based on that, I suspect that, despite Gizmodo’s guessing, the case still is primarily ceramic – although probably more advanced than the earlier iPhones, and with aluminum trim. Ceramic  simply is going to be much tougher and easily made transparent to Wi-Fi signals (and other signals that Apple is probably opting to use), plus can possibly be used for additional sensor applications, such as vibration sensors, pressure sensors, positioners.

Yahoo’s Ben Paterson seems to agree with my assessment about the case, but it’s unclear to me what he is basing his views on.

Regarding the composition of the face of the new phone, little has been written but I think it still is must be Corning’s alkali-aluminosilicate thin-sheet Gorilla Glass, because that is really the best glass interface there is to choose from.

Hopefully we will have more info after Apple’s event in San Francisco. And, if they want someone to test the new iPhone to make sure, I’d be glad to arrange it.