Back again with the second installment of the Knife series!
Now that you guys have learned the basics of knives, we’re going to learn what makes a good one and how to choose ‘em.
Knives on the surface are a very simple tool – it is a sharpened piece of metal with a handle. But anybody who has experience with a knife can tell you there are good ones and there are bad ones. So how can you tell what makes a good knife versus a bad one?
There are literally hundreds if not thousands of different knives in the market from very well-known brands to some nameless brands that can be found at some discount stores. The prices on the knives can range from a few dollars to several hundreds of dollars a knife. So yes, it can get confusing if you don’t know what to look for and know how to decide on what’s important.
If we go back to the basics on knives, there are only 3 fundamental characteristics about a knife above all else that it must meet.
- (S)harpness and durability of the edge.
- (S)hape for Purpose and blade width
- (H)andling and balance
With just 3 things to remember, which I have conveniently coined into an acronym SSH, it should be simple enough. However, each one is a study in itself and the details can be quite overwhelming. Just to make this easier to follow along, I will use the Chef’s knife as the knife to do these explanations. The reason we will be using the Chef’s knife, as stated in the first article, is that this is the go-to knife in the kitchen for most of your tasks.
S- Sharpness and Durability
The sharpness and durability of the edge of the knife is of prime importance as this is the factor that determines how well a knife will cut – this is why you need a knife right? We’ve all seen on TV and most have experienced how poorly an un-sharp knife performs on a ripe tomato. The results aren’t pretty to say the least.
Is it just me or do you find infomercials just hilarious with their demonstration of how bad things can get when you don’t have their advertised gadget?
But not all sharp edges last, this is what we call durability. Some knives lose their sharp edge faster than others, leaving you the task of sharpening the knife more frequently. For a knife to be good, the material it’s made of has to be able to achieve a keen edge, but also keep it as long as possible.
What makes one knife sharper than the other? It all comes down to the steel and the heat treating process that the steel undergoes. In order to understand this subject completely, you would have to be a metallurgist and understand things such as steel composition, heat treating and tempering and terms such as grain size, carbide, austenite, martensite, ferrite, and cementite.
Fall asleep yet?
Well this is not a metallurgy course so I will not bore you with this tech speak. Truth be told, many knives out there won’t even say what steel their knives are made from. So let’s look at this from a very pragmatic approach and see what we have to understand from this very complex and technical area to really get a grasp on what makes a good knife steel.
So we already know that the most basic requirement of the knife steel is whether it holds an edge, so let’s try to understand what an edge is. Simply stated, an edge is created when the surface of a material is ground such that the sides intersect at a point as illustrated in the diagram below:
As you can see there are many ways to achieve this edge and each will have its own particular advantages and disadvantages which we will explore later. In theory we would like this tip to be as atomically small as possible to achieve ultimate sharpness. But alas, reality prevents this as the steel that makes up the knife cannot hold together at this small scale. At a microscopic level, steel has a structure similar to a stone wall.
Each stone represents a larger collection of molecules. In steel this is called grain or crystal size and this affects how sharp an edge can be made without it falling apart from being too fragile. If we overlay an edge cross section into the above picture we can illustrate what I mean – the red line is the resulting cutting edge cross section.
By using the stonewall analogy it is easy to see why finer grained steel will result in a material that can achieve a keener edge.
Now that we know what makes a good steel for getting a good edge, let’s look at what makes an edge durable. We now know the the very tip of the knife edge is only a few molecules in size. It would not take a lot of force to wear or ruin this edge if the material itself is not very hard.
Not surprisingly, steel has a hardness rating system to provide an objective measure of the hardness of the material. The typical measure of hardness of steel in North America is the Rockwell Hardness scale. A reasonable hard knife steel will be in the range of 54-58 while a hard steel knife will be in the area of 58-62 and anything harder than 62 will be deemed extremely hard. The only problem with going extreme hardness is the edge will become brittle and striking hard objects like bone may result in chipping the edge.
(S)hape for Purpose and Blade Width
The final detail of the sharpness of the knife is the edge profile itself. What does this mean? Well the edge of the knife has a taper that reaches a point at the cutting edge. Remember this picture:
So along with the grind type there is the edge angle.
The angle of this edge is critical to achieve optimal cutting performance. I’m sure most of you have experienced a paper cut and how it slits through your skin like butter*cringe*.
The reason for this has to do with the very thin edge of the paper and its relative ease in which the thin paper can displace skin – ouch. Well this works for knife edges as well, if the blade edge angle is larger, then more force would be required to push that wedge through material being cut than a blade with an edge angle that is less. But if the angle is too low the blade would become too thin and fragile.
Many western knives will have edge angles of 20-22° (included angle of 40-44°) which is quite strong and durable but many Japanese or Asian knives will have angles of 15-16° bevel (or 30-32° included angle) and have been renowned for their cutting performance. The key question is – can I take a knife that has a 20° or 22° angle and just put on a 16° bevel on it? The simple answer is yes… but – well there is always a but. If the blade grain structure and hardness is not high enough, the edge durability may not be very good. Unfortunately, you will have to find this out through experimentation.
(H)andling and Balance
The last critical factor in a Chef’s knife is handling and balance. The Chef’s knife will often be used for extended cutting and chopping, therefore how the knife handles in extended use is critical. The typical grip forms that will be used on a Chef’s knife are illustrated below:
Grip A is used when making large slicing cuts through large sections of meat.
Grip B would be the general grip that is used for most other cutting tasks with the chef’s knife. The claw grip (Grip C) is used to grip foods when slicing to maintain control of the food item and the blade. For extended use, the balance point of the knife should be right where the handle meets the blade so that the knife is neutral and not blade heavy or handle heavy. Knives that are not balanced will be tiring to use for long cutting tasks. As well, knives that are too heavy are also tiring to use over the long haul – generally, an 8” Chef’s knife should not be over 300g which would be a very heavy knife indeed. On the light side, chef’s knives lighter than 140g will usually be fragile and flimsy. The handle of the knife is extremely important due to the extended use and the multi-grip position.
When holding the knife in Grip A, the handle has to be just large enough to maintain a tight controlled grip of the knife while your fingertips can roll around the handle and just touch the other side of your thumb. If the grip is too small, it will be hard to maintain grip pressure and if too big, it will become tiring to control such a large handle. Therefore, there is no one size fits all when it comes to knife handles.
The edge shape of a Chef’s knife is flat for the first 2/3 of the knife with the last third curved gently upwards towards the spine which is straight out from the handle. This makes the knife ideal for slicing and chopping with a rolling chopping motion.
Here’s a tip, by keeping the front third of the knife in contact with the board and using the back third almost as a guillotine, you can chop through most things like a breeze. The curvature on the front also makes fast work of separating meat from bones over larger bone structures. The blade of the Chef’s knife is relatively inflexible which makes it ideal for chopping through harder vegetables like squash, kohlrabi or melons.
Now that you know what to look for in a good Chef’s knife, the next article will review a sampling of Chef’s knives from lower cost to high end premium and I will show you which ones are my favourites. We also have a valuable give away to a lucky reader of this blog that will be announced around mid March after the Part 5 of this article series.
I’ll be posting what I’ll be giving away and the form to enter in my next post on #FoodTips.
Until we dine again,
-The Piquey Eater
P.S. Practice good form and keep your fingers safe!