Mat Coch writes:

The grey skies painted a miserable picture over the Montreal skyline, perhaps mirroring the atmosphere within the paddock as the Mercedes tyre test saga rumbled on. Although the rain had stopped by the time the first practice session opened for the Canadian Grand Prix, standing water saw many teams opt to complete just an installation lap as the session got underway.

The wet conditions effectively ruled out Pirelli's hopes that teams would test its 'prototype' medium compound tyre, with potential ramifications spilling over on to the British Grand Prix.

As was the case in Monaco, Esteban Gutierrez headed out on track first, leading the pack around as they performed system checks; Caterham's Alexander Rossi, substituting for Charles Pic for the session, was asked to perform radio tests at a number of different spots around the circuit.

The blue walled wet tyres were the order of the day, rooster tales of spray thrown skywards off the sodden tarmac, though a number of drivers braved the conditions on intermediates, including Mark Webber and Paul di Resta.

No time had been set after ten minutes of the session, the circuit having fallen silent as teams busied themselves in the garages. Among them was Ferrari, testing a newly sculptured front wing while next door Red Bull had a development wing which features no less than nine elements.

Sergio Perez was the first to start a timed lap, even if he didn't complete it. Interestingly, as Perez powered down the long back straight on his return to the pits his car was clearly not riding the bumps well, the McLaren looking like it may shake itself to pieces at any moment.

Moments later Gutierrez was back on track, his Sauber looking smoother in the slippery conditions than Perez' McLaren though still bouncing down the back straight as though speeding along a pot holed country lane. Twenty minutes into the session the Mexican driver was the first and only man to have set a time.

Williams, still without a point six races into the 2013 season, spent the early part of the session with flo-viz paint on its cars, the team clearly spending time focussed on aerodynamic work.

Meanwhile Mark Webber was circulating on intermediate tyres, lowering the fastest recorded lap to a 1:27.909 after almost half an hour of the session gone. It pre-empted a number of drivers taking to the circuit on intermediate tyres, the standing water which was a feature early on now seemingly less of a concern.

While drivers looked to switch to the lesser of the two grooved tyres there was no sign of a dry line. Forecasts predicted rain would cease during the session, though low temperatures were not helping the circuit dry quickly.

With cars circulating the times tumbled; Raikkonen went second fastest on a 1:29.245, improving to a 1:28.290 on the following lap while Nico Hulkenberg was a second behind in third place. Still conditions remained tricky, Valtteri Bottas taking to the grass at the Turn 3 chicane after half an hour. Bouncing over the grass the young Finn kept away from the walls, completing the lap without further incident.

Toro Rosso's Jean-Eric Verge headed to the top of the timing screens as the clock ticked down to fifty-three minutes remaining, a 1:26.436 some three tenths faster than Nico Rosberg who'd set the second best lap.

The Monaco winner soon remedied that situation, lowering the benchmark to 1:26.051 as a dry line began to emerge; Marussia radioed Max Chilton telling the Englishman to go seeking puddles down the straights to cool his tyres.

With fifty minutes remaining the top eight drivers were separated by less than sixth-tenths of a second, at least until Rosberg knocked a second out of his previous best to lay the next marker.

Blotting his copybook early in the weekend was Jules Bianchi who appeared to miss his braking marker at Turn 3 before taking to the escape road. A badly executed spin turn saw the Frenchman facing the barrier perpendicular to the direction he should have been going before the team told him to stop the car with an overheating engine.

With half the session over Felipe Massa finally began a timed lap, the Ferrari driver the only man not to have set a time at that point. His first time, a 1:28.186, was good enough for seventeenth.

A little further back Alexander Rossi was quietly going about his business in twenty-first, someway off regular driver Giedo van der Garde. Importantly however the American driver was keeping himself out of trouble in what were tricky conditions.