Cutting Edge: The Knives – Part I

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Knives and cutlery in general, is the most essential thing, after food, in every cuisine. It is the one item that is used to clean, prep, portion and in some older times, to catch the food to be. Nowadays the innovation, sophistication, marketing and engineering has given us a huge selection of knives of many different shapes and sizes and thy have achieved the unachievable, to distract the buyer from the actual knife to the esthetics which although welcome they are not the primary objective. In this tow part series I will try to give the fundamentals to help someone choose the knife that he/she needs with major guide the ergonomics and the usability. In the first part we will focus on the manufacturing of the knife including the anatomy and sharpening/honing, while on the second we will focus on the specialty knives and the applications.
The first knifes were just chips of larger rocks usually flint, obsidian or other glass type of material. Following that, knives or cutting tools, more correct, were made from bones of animals, and occasionally a wooden handle was attached. We had to wait until we enter the copper age to manufacture knives form metal. And that changed it all. Metal was durable, elastic, non breakable, sharpened easily making it the ideal cutting tool. Although millennia had passed since then, the basic knife shape has not changed at all; the material that the blade is made of has changed, making it even stronger, sharper, more flexible and corrosion resistant. However, although the basic knife shape has not changed there are variations, that make huge different on the application each knife is destined to, resulting to a large number of knives, from chef’s knives crab knives. Do we need them all? No. Do we need half of them? No. Knowing the exact effect of the shape of the knife someone can easily determine the application and decide among many different knifes the right one.Before we talk about the blades and shapes, it is worth talking about the material. The majority of the knives is made out of steel. However steel to steel is very different. The basic steel is made of Iron (Fe) and Carbon (C). The ratio of these two elements will determine many of their properties. The higher the ratio the more brittle the knife will be. It also will be harder, more durable and less flexible. On the other side a low carbon steel will be soft, pliable and flexible. Both types will however rust. So in order to avoid rusting Chromium (Cr) is added. For longer lasting and durability titanium (Ti) is added. For a more light weight knife, Magnesium (Mg) is added. Currently there three common alloys used in the knives.

  1. Carbon Steel: An alloy of carbon and iron, it is traditionally used for blades because it is enough to be sharpened easily. It corrodes and discolors easily, however, especially when used with acidic foods.
  2. Stainless steel: It will not rust, corrode discolor and is extremely durable. But stainless steel blade is much more difficult to sharpen than a carbon steel one, once the edge is established, it last longer than the esdge on a carbon steel blade.
  3. High Carbon stainless steel: An alloy combining the best features of carbon steel and stainless steel, it neither corrodesnor discolor and can be sharpened almost as easily as carbon steel. It is now the most frequently used metal for blades.
  4. Sandwich blades: Very frequently used in Japanese knives. A carbon steel blade sandwiched between two stainless steel sheets, exposing only the edge. It combines the best of both worlds, but it is labor intensive to manufacture so they are not as popular.

Recently the last 15 years or so, there are ceramic knives in the market. Ceramic blades are sharp and remain sharp for ever, but can break very easy and since they are white they stain very easy.

The next important factor other than the material is the method of production. This will determine to the great extend many of the knife properties. The oldest method is the stamped method. It is basically starting with e basic blade shape that it is either cut out from a sheet of steel (the more common method nowadays) or it is poured into a mold from a molten steel (the more common method in older times). The blade then is sharpened to an edge. This method, since the material is required to be in a sheet form, gives a somewhat flexible knife that can bend. The blade is usually very thin easily used more bulky materials like cheese wheels and big chunks of meat. The other method is the forged method. Here the basic blade is curved out from a block of steel (stock removal method). Occasionally the blades can be made by hammering the metal (actual forging method). This results in a thicker, heavier blade, that give the knife body and weight that can result in better more efficient cutting on cutting boards.

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The shape of the blade is essential. The blade is doing the actual cutting and therefore is one of the most important characteristics of the knives. The shape of the blade, and by shape we mean the profile of the blade, is choose in combination of the application the material and the method of production. Soft materials like low carbon steels prefer thicker blades. The usual way of creating the blade is the grinding it against a spinning wheel that has some sort of abrasive like carbides or diamond powder, and an oil as lubricant. The uniformity of the abrasive powder and the the quality reflects on the uniformity of the blade. The blade is always achieved by material removal. Recently laser has been employed to remove material and make the blade. Although lasers are very precise, the laser sharpened knives miss something special that hand sharpening can achieve. As you can see on the figure on the right there are three basic blades. A+B). The convex or concave shape that is very hard to achieve but results in a very sharp (concave) or very thick blade (convex). The concave give a blade extremely sharp with very little support since it is very thin on the edge. It is usually used for thick blades that can offer some more support. The convex shape works the opposite way. The blade is not us sharp but has a great support and it is suited to more heavy duty applications. C) The wedge type of blade is the most common and it is find in the majority of the kitchen knives. It is linearly tapered to the end. It is give a good blade, sharp somewhat durable and it is suited for the thinner blades. D) The chisel is a variation of the wedge shape to offer a little more support and durability. It is found to lower quality knives that are made with a less durable materials. It is the choice blade for the serrated knives. This blade type creates teeth that are sharp points and concentrate the pressure on specific points. With exception of bread or tomato knives the serration is found mainly on cheap knives, as a way to make up for the lack of cutting power due to a dull blade.

With materials, production methods and blade shapes, out of the way let’s now focus on the actual knife. The actual knife that regardless the applications will have some or all of the following characteristics. (image and table from wikipedia)

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APoint:The very end of the knife, which is used for piercingBTip:The first third of the blade (approximately), which is used for small or delicate work. Also known as belly or curve when curved, as on a chef’s knife.CEdge:The entire cutting surface of the knife, which extends from the point to the heel. The edge may be beveled or symmetric.DHeel:The rear part of the blade, used for cutting activities that require more forceESpine:The top, thicker portion of the blade, which adds weight and strengthFBolster:The thick metal portion joining the handle and the blade, which adds weight and balanceGFinger Guard:The portion of the bolster that keeps the cook’s hand from slipping onto the bladeHReturn:The point where the heel meets the bolsterJTang:The portion of the metal blade that extends into the handle, giving the knife stability and extra weightKScales:The two portions of handle material (wood, plastic, composite, etc.) that are attached to either side of the tangLRivets:The metal pins (usually 3) that hold the scales to the tangMHandle Guard:The lip below the butt of the handle, which gives the knife a better grip and prevents slippingNButt:The terminal end of the handle

One of the more important aspects to consider is the tang which is the portion of the metal blade that extends into the handle, giving the knife stability and extra weight. It many knives it is extended to the end of the handle giving the knife strength. In many knives the tang is a thin strip, extending halfway in the handle, riveted with a couple of pins. This can create pressure points while cutting resulting in some cases the snapping of the blade off the handle posing a major hazard.

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One topic that should be discussed here before going to the second part is the sharpening of the knives after using it for a while. There are two types of damages that a knife can suffer. The first is the blade bending like seeing here going from A to b. This can be fixed at home with a honing steel, depicted here.

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The purpose of the honing steel is to straighten the edge and not to sharpen. Start with the knife on an angle going from top to bottom like trying to peel the steel 5 times on each side. Repeat for 4, 3, 2, 1 till you are done. Sharpening now is the damage shown in C to D where the blade has actually chipped off, missing material and therefore it has lost its cutting edge (!). This is fixed with material removal and only. No honing. Although there are in the market many sharpening devices, I am not going to talk about them. Sharpening is something that should be done with grinding wheel by professionals. There are no devices that can substitute either of the two.

With these on mind we can now see the more specific knives that are required for each job and creat a home arsenal of knives that can deliver cutting edge where needed. Stay tuned for more knives to come.

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Last modified: November 21, 2013 by Georgios Pyrgiotakis