by Tim Hayward
6. SAWING CUT. If you’re holding a serrated bread knife and slicing some stale bread, a sawing motion is OK. If you’re sawing with any other kind of knife, it’s blunt and you need to stop and sharpen it.
These are all descriptions of vertical cuts but all can be achieved at various angles to the board.
7. HORIZONTAL CUT. Horizontal cuts are not common in Western cooking and they’re the only ones where the claw is not used. When brunoising onions, a couple of partial horizontal cuts are necessary and these are achieved – with extraordinary care – while pushing the onion half to the board with the fingertips, keeping the rest of the hand high and away in case the knife slips. The other main horizontal cut is the utterly lethal and desperate ‘last slice’ cut, in which a piece of (usually) bread or meat is squashed flat to the board with the palm of the hand, the fingers stretched back and up in fervent but usually futile hope, and the blade sawn between hand and board.
I realise that there are occasions in even the best kitchens when the last piece has to be stretched to two portions, but for me, this particular cut has too many options for horrific slips. The cai dao is used with a raised chopping block that gives knuckle clearance when the blade is used horizontally. As a result horizontal cutting is safer, easier and much more common in Chinese kitchens.
THE CLAW
It would be natural to assume that the knife is a ‘one-handed’ tool but in reality all cutting involves the other hand, offering material up to the blade and stabilising it during the cut. As important as the grasp on the knife itself is ‘The Claw’ – using the tips of the fingers and the backs of the fingernails to hold the food steady and creating a flat vertical surface with the ‘middle phalanx’* along which the flat of the knife can slide. The tips of the fingers are rolled back towards the palm meaning that, in normal use, the knife cannot possibly cut them.
The claw means you can make an extremely rapid chopping action while gently sliding the food past the knife with your fingernail – the wonderful flashy trick of onion chopping so beloved of TV chefs.
Practise the claw whenever you can because without this strange gesture of your spare hand, even the best knives in the world are useless.
* Working backwards from the tip, your finger has three phalanges – distal, middle and proximal.
ON MATERIALS
IN ITS MOST BASIC FORM, knifemaking began with naturally occurring rocks. Flint, found in areas of sedimentary rock, and obsidian are brittle rocks that, because of their molecular structure, break with a characteristic conchoidal or ‘shell-shaped’ fracture pattern.* Bash a couple of pieces together and you’ll notice how the cracked edges conspire to create a lethally sharp, naturally serrated blade, easily sharp enough to cut raw meat or to car ve bone and wood. As the earliest humans developed flint-knapping techniques, various cultures created stone knives of increasingly refined shape and delicacy, but the cutting edge was the result of the original, natural fractures. The edge could never be improved by polishing or grinding, at least not with Stone Age methods, and, though the elegant, highly wrought knife of a chieftain might look impressive when tucked into his antelope-skin belt, it would never be substantially better at doing its job than a freshly cracked rock. Yet the fact that the earliest toolmakers were already creating knives in which beauty was, to some degree, more important than pure function must imply that they were already beginning to imbue them with more abstract values.
Copper and bronze knives appeared as man discovered how to work with these new materials, but these earliest metals were easy to extract and refine because of their softness. A soft metal can make a light arrowhead or a serviceable stabbing weapon but is worse than hopeless at holding a working cutting edge. Even once bronze was created, the best thing for cutting up meat may still have been a flint knife. With the arrival of iron, though, we start to see edged knives with real potential.
Extracting iron from ore, a process known as smelting, involves heating it, melting it and driving off impurities. This is the basic process that begins with rock and ends with rough metal, but it is only the beginning of a series of actions that can alter the qualities of metal in innumerable ways. Smelted iron – sometimes called ‘pig iron’ – is hard, can be cast into shapes and can be strong but it’s extremely brittle. You could cast a knife in iron but if you dropped it on a hard surface, it would probably break. Steel, on the other hand, an alloy of pure iron with up to 2 per cent carbon, is strong and flexible. It is both malleable, meaning it can be pressed into shape without shattering, and ductile, meaning it can be stretched into shape without snapping. The qualities that matter most in a knife are its resistance to snapping, the ability to take an edge, how long the edge lasts, and how easy it is to resharpen. Perhaps less vital to function but no less important to the owner will be resistance to corrosion and aesthetic beauty.
* The pattern is caused by the shockwave which moves from the point of impact like ripples on a pond. As cracking in rocks caused by temperature change occurs in flat planes, the presence of conchoidal fracture patterns in rocks is often accepted as an indicator of human intervention.
By varying the amount of carbon it’s possible to create steels along continua of hardness, flexibility and workability. Alloying it with small percentages of other metals can also alter its colour and durability.
Iron and steel can be cast, that is, poured when molten into a mould and allowed to harden, or they can be forged, which means that a piece is heated until soft and then forced into shape, either by pressure or beating. The rough piece out of which a blade is made could be moulded from molten metal, beaten out of hot lump with hammers, squeezed flat between vast rollers, stretched like noodles or even extruded, like white-hot toothpaste, through a shaped hole. Each of these techniques alters some of the qualities of the original material, as do various heat treatments. Steel, in fact, though a metaphor for permanence, solidity and purity, is, within its parameters, an infinitely variable substance.
Look at a machine-made knife, perhaps a Wüsthof Dreizack Classic 4584/26 like the one. A blank of steel, an alloy containing exact ratios of chromium (Cr), molybenum (Mo) and vanadium (V) with a laboratory-tested Rockwell Hardness of 56, has been carefully selected for its material virtues. It has been forged by giant machines exerting unimaginable force, ground by computer-guided mills precise to the micron in their choreography. The heat treatment will have been controlled to a hundredth of a degree and the finished blade tested to unimaginably high standards. If, like me, you get excited by tech, then this is one of those objects that represents the pinnacle of what human science, design and technology can achieve. To hold it in your hand is to grasp all of that. Like a replacement human joint or an engine component in a million-dollar jet fighter, every single knife coming off the line will be identical – and these are some of the most gorgeous knives in the world, utterly efficient and surgically fit for purpose.
Now consider a knife made in another tradition. A hard steel for a sharp edge is wrapped like a sandwich in a softer, less brittle steel. For an hour or so it’s hammered flat by a man who’s guided by no more complex computer than the one in his own skull. His ‘pattern’ is experience. The temperature control for heat treatment is his judgement of the colour that the metal glows. He will beat the hot sandwich of metal until molecular change is wrought between the layers. Carbon from his furnace will combine with the metal surface and the crystalline structure of the metals will, in places, be re
aligned by the blows of his hammer. This knife will never see a lab, no one could call its material anything as homogenising as ‘CroMoV’, and the final measure of its hardness will be not Rockwell, but the cook who takes it home. If you are excited by craftsmanship then this is one of those objects that represents a whole civilisation’s evolution of creativity and ingenuity, and the expression of an individual artist’s skill. These are some of the most beautiful knives in the world, no two alike at any level, challenging to use, a chore to maintain and breathtakingly beautiful.
HEAT TREATMENT
Traditionally, heat-treating metal meant placing it in a forge until the temperature, judged by colour, was correct, then ‘quenching’ it in water or oil. This rough process conveniently serves to harden steel or cast iron. What is actually happening is that the microcrystalline structure of the metal is being altered and it can be done with much more refinement. Holding metal at certain high heats over varying periods of time or precisely controlling cooling can alter the qualities of the metal in much more subtle ways.
I visited a modern heat-treatment plant to watch some knife blanks being treated. It was a low-rise workshop on an industrial estate outside Derby, nondescript and anonymous from the outside but – with dripping, crusted pots of molten cyanide salt in rows, chains dangling from the ceiling on blood-chilling hooks and a constant throbbing roar like the mouth of a jet engine – a circle of medieval Hades within. It wasn’t, however, served by sweating demons or kobolds stripped to their loincloths, but by a nice chap called Simon. Here, he explained, they can make almost any metal do almost anything. By heating to many thousands of degrees in those pots of molten salt, they can control the chemical content and molecular structure of components to incredible tolerances.
‘What d’you reckon that is?’ he asked, throwing me a dull, matte grey metal mushroom with an inexplicable and disturbing weight to it… ‘Once that’s got the thread turned into it, it’ll be the bolt that holds down the lid on a transport vessel for nuclear waste.’
Our bunch of blanks was heated gently up to around 500°c in an empty pot. ‘Just a warm bath to get them used to the idea,’ said Simon, before they were lowered into a molten salt bath at around 1200°c for 10 minutes. Tiny motes flickered spontaneously on the surface as we watched. It was absurdly pretty but the temperature was like nothing I’ve ever experienced, a manifestation of heat that made the air feel too solid to breathe. Simon lifted the blades clear of the salt bath, danced them across the workshop floor like live fish on a rod and lowered them carefully into a vast tank of sinister black oil which seethed malevolently as they cooled.
This is not, perhaps, the way small craftsman knifemakers have worked in the past but they are beginning to experiment. Imagine a big chef ’s knife that can bend centimetres off-centre and spring straight back. Imagine an entirely rigid blade that doesn’t need a thick, heavy spine. The possibilities are thrilling.
There is currently a huge resurgence of craft knifemaking across the world – not just, as one might expect, in Japan. Craftsmen like Bob Kramer in the States or Joel Black in the UK, collectives like Doghouse or Blenheim Forge are turning out amazing blades bursting with character, buzzing with spirit.
In use, it’s hard to choose between the awe-inspiring technology and precision that go into an engineered knife and the craftsmanship that goes into a hand-built one, but I wanted to find out more about the process. I needed to make a knife.
ON MAKING A KNIFE
THE BLADE BEGINS with a drift of steel pieces, like thick foil. You can cut them to shape with a straightedge and a Stanley knife. We count them and then carefully stack them on to the end of a steel bar. With a few swift passes of a small welding torch they’re roughly stitched together, like a mille-feuille pastry on the end of a stick.
Outside the workshop, ranged along a scarred bench, is the forge, made from an old propane cylinder, on its side and raised on metal legs. The top has been cut out and the inside lined with a thick blanket of mineral wool. A gas pipe, attached to a regulator and shoved through a hole in the side of the cylinder, wakes with a woof and within minutes the forge is glowing – a roaring maw, pulsing between orange and white through a disorientating heat haze. I shove the laminated metal stack into the forge and maneuver it close to the flame. Soon it too is glowing, so I withdraw it and sprinkle the glowing tip with borax, then thrust it back into the heat.* The borax melts and bubbles and, after a few more dustings, we lift the glowing lump into the forging press.
At its heart, the forging press is a hydraulic ram, the kind of thing you’ll see lifting the back of a dump truck or the arm of a digger. Around this is welded a frame of square-section steel girders so the entire pressure of the ram is applied to closing two steel blocks together in an area about the size of a bar of chocolate.
A hydraulic ram this size might easily lift a large car on to a truck. Imagine that pressure applied against an immovable surface. Imagine your fingers trapped in there... no, maybe not. But the pressure is certainly enough to begin squashing the glowing hot metal plates together. Each actuation of the ram crushes the metal sheets tighter and tighter together until they begin to unify. Maybe twenty times we lift the metal from the forge to the press, sprinkle it with borax and crush it again with the whole power of the ram.
Now the metal sandwich is a homogenous piece and the hand-forging can begin. We hold the metal in the flame until it’s glowing madly, then lift it out on to the anvil and clobber it with a short sledgehammer.
* Borax (Sodium tetraborate) is a salt of boric acid and is used as a flux. It lowers the melting point of iron oxide, which allows it to burn off. Unrefined borax is sometimes called tincar, which may give us the word ‘tinker’ for an itinerant tinsmith. Borax is also used as a food-preserving salt and may have been the ‘natron’ used to preserve some of the bodies of the pharaohs.
I had thought, before today, of red-hot metal as flexible, perhaps the consistency of hard Plasticine, but, in reality it’s still hard. Heat, at this level, only softens the metal a little. Essentially, you’re wailing away at something only marginally softer than the solid, cold metal of the anvil, but with the added frisson of terror that, at this temperature, it could burn through clothing and flesh in micro-seconds. The upside to this is that it’s hard to go wrong: no single blow with the hammer is sufficient to truly mess up your blade. On the other hand, repeating the same blow again and again is beyond exhausting.
I’m not a small man; in fact, I’m probably built bigger than the knifemaker, but after 20 or so blows I can hardly swing the hammer; my forearm begins to cramp and my shoulders scream. The professional steps in and shows me how to let the hammer fall – just guiding it gently, letting it bounce and only putting in the smallest effort at the very top of the swing.
With this technique it’s possible to keep hammering for much longer; I reckon it takes around 200 blows between us before the blade is roughly in shape.
Now we quench the hot blade in oil, a process that hardens the knife a little, then we draw on to it with a Sharpie, tracing the shape of the blade from a cardboard template. Using a huge pair of bench mounted shears with a long handle for leverage, we nip away spare shards of the beaten blade to create the correct ‘profile’. Now it is time to take it to the wheel.
The wheel is about a metre and a half in diameter and 15 centimetres (
6 inches) thick, mounted in a wooden frame, half boxed in and equipped with a powerful electric motor at its axle. The motor starts and over five minutes, it slowly comes up to speed. The wheel weighs only a little less than I do and it’s now spinning at 7,000 rpm. When the power is switched off it will take nearly 15 minutes to slow to a halt. If it were to break loose from its bearings it would crash through the brick wall it faces (and possibly the two neighbouring houses). I must lie along the casing and over the wheel.
A water spray cools the surface and keeps down the dust but it still feels terrifying to be lying face down on something so powerful and applying steel to its surface just inches from your face. Slowly, in showers of water, steam and spark, the blade begins to take shape. Again the process is slow. The metal is abraded slowly so it’s easy not to push things too far.
There is more to be done to the blade by hands much more skilled than mine but it now looks the part. It’s an ugly thing – dark, matt, rough-surfaced and crude but there’s something else, something much more powerful. In a few hours I have watched thousands of joules of energy pour into this lump of metal. Thousands of degrees of heat, tons of hydraulically applied pressure and the hundreds of hammer blows that had completely exhausted my upper body. Of course, I know enough physics to explain exactly how the energy was disseminated and yet, the feeling of it remains in the blade. It feels like if I could find the right switch, all that power might stream back out, like some kind of culinary light-saber.