Apple, which rolled out its much-delayed white iPhone in 28 countries on Thursday, has said it had made changes in the manufacturing process to make the new gadget more durable.

It's not as simple as making something white, Schiller said. There's a lot more that goes into both the material science of it--how it holds up over time...but also in how it all works with the sensors, Apple Senior Vice President Phil Schiller told All Things Digital.

Meanwhile, it was reported on Thursday the white iPhone was sold out in one day in Beijing. Not jus in China, the new device was reportedly moving rapidly in across Asia. Local papers in Hong Kong also reported that the phone sold out within the first hour.

Apart from Apple's claim over increased durability, the new gadget reportedly has some differences with the regular models, the most notable being its slightly thinner frame. However, CNET reported that Apple did not immediately respond to a query on size difference between the two models.

The CNET report had this to say: The white version of the iPhone 4 sports a clearly noticeable version of the proximity sensor, which sits just above the top speaker grille. On the black models, this is a detail that disappears with the rest of the bezel. Early imagery of the white iPhone 4 had that sensor appearing as a fine mesh of dots, akin to the way the company hides notification lights on its notebook computers.

Schiller said the white iPhone now has extra protection against UV. While launching the iPhone 4 in June last year, Apple had announced it would soon launch a white version of the phone. However, the tech giant postponed the launch of the white version several times and rumor mills suggested that manufacturing issues had cropped up every time.

According to PCWorld, Apple co-founder Steve Wozniak had admitted early this year that there were some manufacturing issues with the white iPhone, and that these were resolved.

It was rumored that issues with paint had played spoilsport in Apple's plans to launch the white iPhone. AppleInsider had reported earlier in the year that the tech giant had approached a Japanese company to prepare a new paint material specifically for the white iPhone.