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Jun. 05, 2014

Getting an Edge on Razors

by Mark Miodownik

Click to enlarge images
Listen to author Mark Miodownik chat with SciFri about Stuff Matters.
 
I had never been asked to sign a non-disclosure agreement in the bathroom of a pub before, so it came as something of a relief to discover that this was all that Brian was asking me to do. I had met Brian for the first time only an hour earlier. We were in Sheehan’s, a pub in Dun Laoghaire that wasn’t far from where I worked at the time in Dublin. Brian was a red-faced man in his sixties with a walking stick for his bad leg. He was smartly dressed in a suit and had thinning gray hair with a yellowish tinge. He chain-smoked Silk Cut cigarettes. Once Brian found out that I was a scientist he guessed rightly that I would be interested to hear stories of his life in London in the 1970s, when he was in the right place at the right time to trade Intel 4004 silicon chips, which he imported in boxes of 12,000 for £1 each and sold in small batches to the fledgling computer industry for £10 each. When I mentioned that I was researching metal alloys in the Mechanical Engineering Department of University College Dublin, he looked pensive and was quiet for the first time. I took this as an opportune moment to head to the bathroom.
 
The non-disclosure agreement was scrawled on a piece of paper which he had clearly just ripped out of his notebook. The contents were brief. They stated that he was going to explain his invention to me but I had to keep it confidential. In return he was to pay me one Irish pound. I asked him to tell me more, but he comically mimed the zipping of his lips. I wasn’t quite sure why we had to have this conversation in a bathroom stall. Over his shoulder I saw other drinkers come in and out of the bathroom. I wondered if I should cry out for help. Brian searched in his jacket and got out a pen. A scruffy pound note emerged from his jeans. He was very insistent.
 
I signed the paper against the graffiti-daubed wall. He signed too, gave me the pound, and the slip of paper became a legal document.
 
Back by the bar with our drinks, I listened as Brian explained that he had invented an electronic machine that sharpened blunt razor blades. This would revolutionize the shaving business, he explained, because people would need to own only one razor in their lives. At a stroke it would put the billion-dollar industry out of business, make him an exceptionally rich man, and reduce consumption of Earth’s mineral wealth. “How about that?” he said, taking a triumphant gulp of his pint.
 
I eyed him with suspicion. Sooner or later every scientist has his ear bent by someone with a crackpot idea for an invention. In addition, razor blades were a sensitive subject for me. I felt prickly and uncomfortable as I became aware of the long scar down my back, the result of my encounter on the platform at Hammersmith station. But I gestured for him to continue and kept listening...
 
It is an odd fact that steel was not understood by science until the 20th century. Before that, for thousands of years, the making of steel was handed down through the generations as a craft. Even in the 19th century, when we had an impressive theoretical understanding of astronomy, physics, and chemistry, the making of iron and steel on which our industrial revolution was based was achieved empirically—through intuitive guesswork, careful observation, and a huge slice of luck. (Could Brian have had such a slice of luck and simply stumbled upon a revolutionary new process for sharpening razor blades? I found that I wasn’t prepared to dismiss the idea.)
 
During the Stone Age, metal was extremely rare and highly prized, since the only sources of it on the planet were copper and gold, which occur naturally, if infrequently, in the Earth’s crust (unlike most metals, which have to be extracted from ores). Some iron existed too, most of it having fallen from the sky in the form of meteorites.
 
Radivoke Lajic, who lives in northern Bosnia, is a man who knows all about strange bits of metal falling from the sky. Between 2007 and 2008 his house was hit by no fewer than five meteorites, which is statistically so hugely unlikely that his claim that aliens were targeting him seems almost reasonable. Since Lajic went public with his suspicions in 2008, his house has been hit by another meteorite. The scientists investigating the strikes have confirmed that the rocks hitting his house are real meteorites and are studying the magnetic fields around his house to try to explain the extremely unusual frequency of them.
 
In the absence of copper, gold, and meteoric iron, our ancestors’ tools during the Stone Age were made of flint, wood, and bone. Anyone who has ever tried to make anything with these kinds of tools knows how limiting they are: if you hit a piece of wood it either splinters, cracks, or snaps. The same is true of rock or bone. Metals are fundamentally different from these other materials because they can be hammered into shape: they flow, they are malleable. Not only that, they get stronger when you hit them; you can harden a blade just by hammering it. and you can reverse the process simply by putting metal in a fire and heating it up, which will cause it to get softer. The first people to discover these properties 10,000 years ago had found a material that was almost as hard as a rock but behaved like a plastic and was almost infinitely reusable. in other words, they had discovered the perfect material for tools, and in particular cutting tools like axes, chisels, and razors.
 
This ability of metals to transform from a soft to a hard material must have seemed like magic to our ancient ancestors. It was magic to Brian too, as I soon found out. He explained that he had invented his machine by trial and error, with no real appreciation of the physics and chemistry at play, and yet it seemed that he had somehow succeeded. What he wanted from me was to measure the sharpness of the razors before and after they had been through his process. Only this evidence would allow him to begin serious business discussions with the razor companies.
 
I explained to Brian that it would take more than a few measurements for them to take him seriously. The reason is that metals are made from crystals. The average razor blade contains billions of them, and in each of these crystals the atoms are arranged in a very particular way, a near-perfect three-dimensional pattern. The bonds between the atoms hold them in place and also give the crystals their strength. A razor gets blunt because the many collisions with hairs that it encounters force bits of these crystals to rearrange themselves into a different shape, making and breaking bonds and creating tiny dents in the smooth razor edge. Resharpening a razor through some electronic mechanism, as he proposed, would have to reverse this process. In other words, it would have to move atoms around to rebuild the structure that had been destroyed. To be taken seriously, Brian would need not just evidence of such rebuilding at the scale of the crystals but a plausible explanation at the atomic scale of the mechanism by which it worked. Heat, whether electrically produced or not, usually has a different effect than the one he was claiming: it softens metal crystals, I explained. Brian was adamant that his electronic machine wasn’t heating the steel razors.
 
It may be odd to think that metals are made of crystals, because our typical image of a crystal is of a transparent and highly faceted gemstone such as a diamond or emerald. The crystalline nature of metals is hidden from us because metal crystals are opaque, and in most cases microscopically small. Viewed through an electron microscope, the crystals in a piece of metal look like crazy paving, and inside those crystals are squiggly lines—these are dislocations. They are defects in the metal crystals, and represent deviations in the otherwise perfect crystalline arrangement of the atoms—they are atomic disruptions that shouldn’t be there. They sound bad, but they turn out to be very useful. Dislocations are what make metals so special as materials for tools, cutting edges, and ultimately the razor blade, because they allow the metal crystals to change shape.
 
You don’t need to use a hammer to experience the power of dislocations. When you bend a paper clip, it is in fact the metal crystals that are bending. If they didn’t bend, the paper clip would be brittle and snap like a stick. This plastic behavior is achieved by the dislocations moving within the crystal. As they move they transfer small bits of the material from one side of the crystal to the other. They do this at the speed of sound. As you bend a paper clip, you are causing approximately 100,000,000,000,000 dislocations to move at a speed of thousands of hundreds of meters per second. Although each one only moves a tiny piece of the crystal (one atomic plane in fact), there are enough of them to allow the crystals to behave like a super-strong plastic rather than a brittle rock.
 
The melting point of a metal is an indicator of how tightly the metal atoms are stuck together and so also affects how easily the dislocations move. Lead has a low melting point and so dislocations move with consummate ease, making it a very soft metal. Copper has a higher melting point and is stronger. Heating metals allows dislocations to move about and reorganize themselves, with one of the outcomes being that it makes metals softer. Discovering metals was an important moment in pre-history, but it didn’t solve the fundamental problem that there wasn’t very much metal around. One option, clearly, was to wait for some more to drop from the sky, but this requires a huge amount of patience (a few kilograms fall to the surface of the Earth every year, but mostly into the oceans). At some point humans made the discovery that would end the Stone age and open the door to a seemingly unlimited supply of the stuff. They discovered that a certain greenish rock, when put into a very hot fire and surrounded by red-hot embers, turns into a shiny piece of metal. This greenish rock was malachite, and the metal was, of course, copper. It must have been the most dazzling revelation. Suddenly the discoverers were surrounded not by dead inert rock but by mysterious stuff that had an inner life.
 

Excerpt from Stuff Matters by Mark Miodownik. Copyright © 2013 by Mark Miodownik. Used by permission of Houghton Mifflin Harcourt Publishing Company. All rights reserved.

 
About the Author
Mark Miodownik recently appeared in The Times' inaugural list of the 100 most influential scientists in the U.K. He is professor of materials and society at UCL and presenter of several BBC television documentaries, including How it Works and The Genius of Invention, as well as appearing as scientist-in-residence on Dara O Briain's Science Club. In 2010, he gave the Royal Institution Christmas Lectures. He is director of the UCL Institute of Making which is home to a materials library containing some of the most wondrous matter on earth, and has collaborated to make interactive events with many museums, such as Tate Modern, the Hayward Gallery and Wellcome Collection.
 
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About Mark Miodownik

Mark Miodownik recently appeared in The Times' inaugural list of the 100 most influential scientists in the U.K. He is professor of materials and society at UCL and presenter of several BBC television documentaries.

The views expressed are those of the author and are not necessarily those of Science Friday.

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