Ahead of today's second free practice session the air temperature is 25 degrees C, while the track temperature is 38 degrees. It remains nice and sunny.
McLaren set the pace this morning, the Woking outfit taking a brave gamble in running a wing set-up that sacrifices straight-line top speed for downforce through the corners.
Tyre options this weekend are hard (prime) and soft (option), however we saw little of the option tyres this morning.
All teams that have them were running the F-duct this morning, with Toro Rosso using its version for the first time.
The lights go green and Alguersuari leads the way, followed by Petrov, Yamamoto, di Grassi and de la Rosa. Webber, among the first to go out, performs a practice start at the end of the pitlane.
Bruno Senna, who has virtually no running this morning due to a brake problem, appears to have encountered more bad luck as his car grinds to a halt shortly after leaving the pits. The marshals push the car to safety.
Alguersuari posts 27.950 but this is almost instantly eclipsed by Petrov who crosses the line at 25.290.
Just five minutes into the session there are 16 cars on track as Kubica posts a 24.822 to go quickest. Teammate Petrov flat-spots his front-right tyre as he locks up going into the first chicane.
A 24.612 sees Alonso go third as Button takes fourth, ahead of Petrov, de la Rosa, Liuzzi and Sutil. Shortly afterwards, Schumacher runs wide and off into the gravel at the beginning of the Parabolica.
As Buemi goes quickest in the first sector, Button goes quickest overall, crossing the line at 24.062. A poor final sector means that Buemi can only manage seventh (24.809).
Alonso improves with a 24.264 as Button consolidates his top spot with a 23.296 having gone quickest in sectors two and three.
Seventeen minutes into the session all but Senna, Vettel, Glock and Hamilton have posted times. The crew is working on Hamilton's car in the McLaren garage having opted to run the car without the F-duct. Button, on the other hand, will continue with the device.
Webber, having posted a personal best in S2, improves from twelfth to ninth with a 24.781.
Hamilton goes second with a 23.869 - 0.573s off his teammate's pace - leaving McLaren with the dilemma or running with or without the F-duct for the remainder of the weekend.
A couple of laps later, despite looking slightly wobbly on the run to Parabolica, Hamilton closes to within 0.065s of his teammate's time. Then again, as he closes to within 0.023s of his teammate, it could be the buffeting the camera is getting. The Englishman is also running significantly less wing.
A 23.154 sees the 2008 champion go quickest, out-pacing the 2009 champ by 0.142. Alonso remains third ahead of Vettel and Kubica.
Watching his monitor in the Red Bull garage, Sebastian Vettel looks suitably worried as Hamilton and Button continue to dominate. The German is currently 0.801s off the pace, his teammate 1.519s.
Forty minutes into the session, Vettel is back on track, weaving from side to side in an effort to generate more heat into his tyres. Elsewhere, Massa and Webber both improve to seventh and eighth respectively.
At half-time, it's: Hamilton, Button, Alonso, Vettel, Kubica, Rosberg, Massa, Webber, Hulkenberg and Sutil.
Mass, having improved to fifth with a 24.100, posts personal bests in sectors one and two, finally crossing the line at 23.891 to go third. Nonetheless, he remains 0.737s off the pace of the McLarens.
The McLaren duo is on track, both on the option (soft) tyre, as is Trulli. After a couple of laps with no significant improvements, Hamilton goes quickest in S1. However, a poor final sector means he fails to improve.
With 34:17 on the clock Bruno Senna climbs back into his car. Meanwhile, Hamilton heads back to the pits having damaged the endplate on his right-front wing.