On the last dive of the trip, one of the Mirs came across a chunk of metal that looked like a part of the hull. The scientists had agreed beforehand that they would bring up no human artefacts; they felt that the site should be consecrated as a burial ground, and that retrieval of personal items would smack of grave robbing (Nic: an opinion I do not agree with). But for strictly scientific purposes, they did want to bring up a sample of hull.
And there it was, resting on a ripple of the ocean floor silt as though placed there the previous month: a frisbee size chunk an inch thick, with three rivet holes, each an inch and a quarter across. Back aboard the mother ship, with the surface grime carefully squirted off the piece with a high pressure water jet, researchers were surprised to see remnants of the original paint.
By now, that piece of steel should have corroded nearly to oblivion. But when a metallurgist saw it later, he had an immediate explanation: "OF course: there's no oxygen down there." Then Blasco pointed out that fish were swimming about, and the metallurgist stopped talking.
Sow how could there have been so little corrosion? "It somehow involves temperature and pressure" says Blasco, "That's not a very good explanation, but it's all we have for now."
Of even more interest to those intrigued by the question of the ship's unseemly rapid sinking was the condition of the edges of the hull piece: jagged, almost shattered. And the metal itself showed no evidence of bending. High quality ship steel, metallurgists know, has a lot more give, more ductility, than most people imagine, and probably wouldn't break. Yet the edges of this sample looked almost as though they were made of broken china.
Three years later, now in the Halifax testing lab, I pick up that hunk of the Titanic from a work table. It's been sitting there among broken gears, split I-beams and ruptured flanges from other ships, representing various naval problems, and it looks like junk. I remind myself that its the only one of its kind in the world. The 80 year old paint is splotchy brown, with an underlying smear of lead oxide, now a pinkish orange.
One edge is ruler straight and shiny, where a strip of metal has been sliced off. A few test pieces, cigarette sized "coupons" have been fashioned from the strip. Some have already been destroyed in preliminary testing in another government laboratory in Otawa. The last piece will soon be mounted in a device that will conduct what is known as a Charpy test. In the lab are Blasco and another of the Imax team, Duncan Ferguson, a 34 year old mechanical engineer.
The metallurgist in charge is Ken KarisAllen, 35, a government specialist in cracks and corrosion. He's energetic, quick moving, almost taut, and when he speaks of his Charpy machine, he does so with fondness.
A Charpy tests brittleness, he explains, nonchalantly pushing the machine's huge pendulum. Testing is simple: As a coupon is held tightly against a steel holder, the pendulum - 67 pounds and 2.5 feet long - swings down and thumps against the sample, sometimes breaking it. The pendulum's point of contact is instrumented, with a readout of forces electronically recorded in millisecond detail.
KarisAllen will test two coupons: one, a sample of standard good quality steel used in modern ships; the other a slice from the Titanic. "If things go as I foresee," he says, "the first piece will go 'thud.' The second will tinkle."
Both coupons are resting in a bath of alcohol at -1C degrees - to simulate the water temperature of 80 years ago. KarisAllen must rush the test piece from the bath to the holder in five seconds.
He hauls up the weight and locks it in place. "OK?" he asks, and looks around the room. "Here goes."
With a pair of stainless steel tongs, he lifts the first piece from the bath, and whisks it to the holder, reaches quickly to the red release handle and yanks. The pendulum swings down and thuds to a halt. The test piece has been bent into a V shape.
He then repeats the process with the Titanic sample.
This time there is no thump. The pendulum strikes the piece with a sharp "ping," barely slows and continues up on its swing while the sample, broken in two, sails across the room to smack a metal waste basket.
Traces on the computer screen, confirm what the metallurgists suspected, and have now seen: the Titanic's hull steel is brittle. When it met the iceberg, the hull plates didn't bend in they fractured.
The steel is embrittled not from sitting on the ocean floor for most of a century. It was that way when it came from the steel plant, and became even more brittle slicing through that -1C degrees water. "To make present day steel that brittle," says KarisAllen, "I'd have to lower the temperature to -60C - -70C degrees."
"Back then nobody understood the concept of brittle fracture," adds Ferguson. "They tested the steel for strength [the maximum stress a material can stand before it breaks], and if it passed, that was that." What they did not know then was that high sulphur content makes for brittleness, and Titanic steel was high even for the times. "It's full of sulphide occlusions called 'stringers,' and it would never get out of the yard today. It wouldn't even make good rebar, which is pretty lousy steel."
Nic: The steel was also compared to a rivet hole 'slug', that was taken as a momento by Edwin Blow Weatherup, an accountant in the Pay Office of the Harland & Wolff ship yards in Belfast. At home he stamped his initials on it. He moved to Canada in the early 1920's where he used the slug as paper weight. A half a century later, when his son Bud, a cook in the cafeteria of the Nova Scotia Research Corp., read about Steve Blasco's research on the Titanic, he remembered the paper weight and told Blasco about it.
The Halifax researchers were delighted when Weatherup lent it to them. A comparison between it and the segment retrieved from the Titanic would reveal any changed that had been wrought on the hull as a result of 80 years in frigid temperatures at 6000 psi pressure.
Metallurgist Ken KarisAllen carefully shaved off a sliver off the divot's side, shaved a similar piece of the Titanic hull piece, and put them both under a comparison microscope. The cell structure, grain and chemical composition, over all those years had remained identical.