Everyone understands the purpose of a knife, but when it comes to sharpness, it is far from obvious.
One of the most telling parameters of any knife is, of course, its sharpness in the first place, and in the best case it should be able to cut everything, well almost everything. For example, the knife should be able to cut bread, roast meat, ripe tomatoes. It should be able to cut frozen food from time to time and it should be able to cut bones, at least chicken bones. If such a knife is reasonably priced, it will be the sharpest knife in the world.
Do you think that a list like this is a bit too much? Can a knife really handle the whole combination of products? Anyone who is familiar with all these products will probably realise that the cut of all the products will be quite different.
The right question to ask is what characteristics, steel a knife should have in order to be convenient and efficient in cutting all types of food. In theory, a truly sharp knife should do the job, but there are different levels of sharpness.
In many ways obsidian, or as they often say volcanic glass, is made of silicon. According to some reports, the thinnest blade was created from obsidian flakes 3 nanometres thick, equal to 0.003 microns. Such a thin and sharp blade is beyond imagination.
These scalpels are many times sharper than the usual surgical instruments, but due to their fragility and the fact that they leave tiny fragments after cutting, they are forbidden from using for surgery.
Stepping back from the unimaginable things - the sharpest steels are those that have a high level of hardness after hardening. However, as the hardness and sharpness of steel increases, this kind of steels inevitably become brittle as well.
In case you are interested, you can check out the somewhat unusual attempts to create a modern obsidian blade World’s Sharpest Obsidian Knife
In industry, bimetal steels joining has been developed to ensure that the steel has good cutting characteristics and sufficient resistance of the cutting edge.
We can assume that some readers have held a metal hacksaw or wood saw in their hands - the saw blades are made of exactly that bimetal steels alloy. On one hand the blade has enough teeth and on the other hand it is flexible and thin enough not to overheat and penetrate the material well.
A household knife has a range of common tasks, although the blade of this knife is sometimes used in various unusual purposes.
It is well known that a knife for cutting bread should have a sort of serrated blade, and that the blade for cutting meat should not be very wide. For cutting vegetables, however, the blade should be thin.
You can imagine certain specifications of a knife like this. Such a knife is likely to be about 15 cm long and will have a serrated edge to cut bread crosswise. For cutting or slicing meat, a width of about 20mm will be fine. For slicing vegetables, the thickness of the blade should be maximum 1.5 mm or even less. The blade made of bimetal alloy will have a certain flexibility and resistance of the serrations.
Will such a knife cut through frozen food and bones? Perhaps, but how and how much physical effort it will take is a very difficult question to answer at once. Besides, the worst enemy of thin and sharp blades is ice. Bones can also cause significant chipping and bending of the edge.
Many people probably know that Japanese kitchen knives and knives from Japan in general tend to be a certain benchmark of quality and sharpness.
For example, a classic Japanese kitchen knife with a hardness of around 64 HRC made of white paper steel was carefully sharpened. The measured sharpness was initially about 127 g according to the BESS test. After sharpening at 12000 grits and finishing on leather, the sharpness increased to 27 grams. In other words, the knife became sharper than an ordinary shaving blade. However, how long will this sharpness last?
The result of these simple tests is that the thin cutting edge of the blade can be damaged by eggshells. The reason is simple - the high hardness of the steel and the very thin cutting edge.
To check the sharpness of your knife in domestic conditions, in addition to the common tomato test, there are a number of other tests that will help you to determine the sharpness of your knife. It is true that you must understand that sharpness comes not only from the steel and the right angle of sharpening, but also from the proper sharpening in general.
The easiest and most accessible is the paper test. Paper can be cut crosswise as well as lengthwise, or even at a slight angle to the plane of the sheet of paper. The thinner the paper, the lighter and cleaner the cut, the sharper your knife. Sometimes you can even put a strip of paper bent in half at an angle and try cutting it vertically. This is where only a really sharp knife can do the trick. You can also try running the blade almost along the surface of the paper, and if the blade bites into the sheet on its own, then the knife is also very sharp.
Checking by shaving or cutting free hanging hair (HHT) is also quite common, but does not always show the real picture.
In fact, the sharpness of any knife is determined by the amount of pressure you have to apply when making the cut. It is better to say that the less pressure is applied, or the more efficiently the knife cuts under its own weight, the sharper the blade. You can find this out in numbers only by using a special device, such as the Edge-On-Up PT50A.
Of all the tests available, the Edge-On-Up brand test with the BESS scale (Brubacher Edge Sharpness Scale) is perhaps the most technologically advanced and precise, as the sharpness of your knife and thus the sharpening quality are measured in real figures.
How does this sharpness test work? In the holder of the device there is a thin synthetic wire which must be cut in one movement by placing your knife according to the instructions. A scale located under the wire holder measures the force transmitted at the moment of cutting and this data reflects the result of the test in grams on the device display and is checked against a table.
The BESS unit represents the maximum cutting edge pressure of the knife when cutting certified material. Thus, the lower the applied pressure, the lower the value in grams and the sharper the cutting edge.
There is also room for a bit of cheating, but if done properly and honestly, the results show a realistic picture.
For more clarity and understanding of the sharpness tests, the video The Sharpest Knives You Can't Buy by the Burrfection is worth watching.
The first and most important conclusion is that there is no such thing as a permanently sharp knife - any knife will blunt in the course of use. Secondly, all steels are different and cannot hold a thin cutting edge for the same period of time, so there is no such thing as a universal steel or a universal knife that can handle all materials and products equally well. Thirdly, the quality of the steel, the size of the blade and the complexity of machining all have a direct impact on the price of the knife itself. This is directly related to the quality of the cutting edge and the sharpness of the blade. Therefore, there are no cheap knives of acceptable quality that will last for a sufficient period of time after one sharpening session.
This applies to all cheap steels kitchen knives that are sold in a set. It is better to buy one good knife than several useless ones. It will be a better decision both financially and morally. It will be much more pleasant to have a good knife in the kitchen and to use a good tool that brings you satisfaction.
There is one curious kitchen knife that is promoted as the world's sharpest knife. It is not worth reciting the content in the context of this article, you can just watch the video.
In case you still want to see the sharpest knife, you can check it out in the video titled The World's Sharpest Knife by Ashens (https://www.youtube.com/watch?v=fCQcFM4xrbI). Whether it is worth the money or not, whether you need it or not, is up to you to decide.
And finally, to keep you entertained, you can watch the following videos to get an idea of what you can use to try and make the world's sharpest knife:
The world's sharpest obsidian knife - https://www.youtube.com/watch?v=XYHxjDdHQXY
The world's sharpest plastic knife – https://www.youtube.com/watch?v=GMS6AoXKMeQ
The world's sharpest cardboard knife - https://www.youtube.com/watch?v=jvo86AHovFc
The world's sharpest rice knife - https://www.youtube.com/watch?v=R6_ugobl5sk
The world's sharpest wooden knife - https://www.youtube.com/watch?v=kKH63_r0OCA
The world's sharpest paper knife - https://www.youtube.com/watch?v=RUlHhrL_Zj8
The world's sharpest chocolate knife - https://www.youtube.com/watch?v=D2XNVFlh-DU
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