Mercedes-Benz has revealed that the new SLK, due next year, will get the option of a glass roof panel in its folding hard top. Called the 'panoramic vario roof with Magic Sky Control' it allows the glass to be switched between transparent to opaque in seconds.

The glass panel contains particles that, when subjected to an electrical current, align themselves to allow light to pass through. Turn off the power and the particles assume random positions, turning the roof opaque. A switch on the SLK's roof console controls the process.

Even when transparent the roof reduces the transmission of ultra-violet and infra-red light compared with conventional 'green glass'. To prove its effectiveness Mercedes' engineers tested the system in Death Valley, Nevada. With temperatures of over 50 degrees Celsius the power of the sun was measured at 1,000 Watts per square metre in the open. Under the SLK's clear glass this dropped to 200 Watts and with the glass darkened just 40 Watts passed through.

Mercedes describes the panoramic vario-roof with Magic Sky Control as giving 'a pleasant wellness atmosphere in the vehicle interior'. As far as we can tell that means the driver and passenger can enjoy a light, airy interior; without having to lower the roof.

John Lambert - 10 Nov 2010