Kitchen Knives – Kitchen knife construction part 1.
Understanding quality in kitchen knives can be a challenge. In order to do this, you need to understand the techniques used to give a knife balance and how the various materials, used in their construction, come together in the forging process to create high performing knives.
After reading part one of our guide to kitchen knife construction you should be able to determine if a knife is well balanced and how that balance has been achieved. After briefly discussing kitchen knife steel in our previous post on the basics of kitchen knives we will also be discussing, in detail, kitchen knife steels in this post. We will cover how the steel a knife is made of will dictate how it will perform and how you must care for it.
Knives are the most important tool in the kitchen and regardless of whether you are a professional chef or a home cook you should have good quality and well-maintained knives. A sharp, good quality knife is much safer to work with and yields far better results than poor quality, blunt knives will.
We hope that this article is both useful and informative. This is part two in a series that so far has covered the basics of kitchen knives. Our goal with this series is not to create a guide to forging knives, but an extensive guide to purchasing, using, and caring for them. This guide is for home cooks and professional chefs alike and hopefully serves as a useful resource.
How kitchen knife construction will affect balance and comfort.
There are a number of elements in a kitchen knife which a blacksmith can adjust or manipulate in order to give a kitchen knife balance. The tang for example, which is the metal which extends from the heel end of the blade through the handle, can be made larger or smaller in order to offset the weight of the blade. Some terms you may have heard while shopping for knives are Full Tang, Half Tang and Through Tang. These terms describe how the tang of the knife has been designed. If it is a full tang it extends the full length of the handle and often exhibits the same profile as the handle. A half tang, as you would assume, only runs half the length of the handle. A through tang runs through the centre of the handle and is often not visible. The through tang is often found on Japanese style knives and is generally the smallest tang you will find.
What does all this tell you as a user of kitchen knives. Simply this, on a well-balanced knife the tang needs to offset the weight of the blade and a smaller tang means a thinner, lighter blade and vis-a-versa.
On a long blade, like a Gyuto or a Sujihiki (Slicer), the knife maker only has a limited amount of material at the tang, which can be added to offset the weight, and balance the blade. To overcome this the knife maker will reduce the amount of material at the spine of the blade to reduce the blades weight. Conversely, on smaller knives the blacksmith may remove less material.
Another technique, which is commonly used, is distal tapering. Distal tapering is characterised by a thinning of the blade or the tang or both from the desired balance point to the end of the blade or tang. Distal tapering can also help to create a more desirable and better performing blade geometry. We will discuss blade geometry in part two of our guide to kitchen knife construction.
Which steel is best for me?
In our previous post covering the basics of kitchen knives we introduced the topic of steel and the two main categories of steel, being high carbon steel and stainless steel. We briefly described how each of these two steels perform and the key characteristics that define them. A particular steel is going to perform differently depending on how the blacksmith treats it. Steel manufacturers will imprint a selection of characteristics on a given type of steel. They will then give a guideline, which will help a blacksmith to manipulate the metal to get the desired result they are looking for. Naturally, in factory conditions, each knife will be very similar. As will be the case with experienced blacksmiths. However, it cannot be simply said that a particular steel will perform in a certain way for every knife that is made out of it.
So, with that in mind we are going to follow a different course to that which many other writers have followed. We will still list off a few of our favourite steels and briefly describe their typical characteristics, but instead of focussing on creating a definitive list we will focus on describing the differences between High-Carbon Steel and Stainless Steel and why you might choose one over the other. From our perspective, as chefs and home cooks, all we need to be concerned with are two key points. What is the hardness of the steel and is it stainless steel or high carbon? These two points will define how we must care for a particular knife (cleaning and sharpening) and how we can expect it to perform in terms of sharpness and edge retention.
High carbon steels require regular cleaning during and after use. These steels are susceptible to rust and are particularly vulnerable to highly acidic produce, lemons for example will cause an almost immediate patina to form on the blade of a high carbon steel knife. Professionals who work with these knives often have two cleaning clothes on hand, one wet and one dry. The wet cloth is used intermittently to remove any acidic liquid or produce build up on the blade between slices and the dry cloth is used at the end of a task to ensure the knife is dry between uses. This is a good habit to form, both in terms of your knife’s health and in terms of hygiene and flavour cross contamination. Most professionals should be practicing this process regardless of which type of steel their knives contain.
If you plan on storing your high carbon steel knives for an extended period, you should coat them with some form of protective oil (Camellia Oil or Tsubaki Oil). Moisture in the air will eventually cause rust and an oil coating is a good way to protect them for longer periods. Although not as important, stainless steel knives (actually only stain resistant) could also benefit from this.
Regardless of how well you care for your high carbon steel knives they will eventually develop a patina and if you do not care for them properly, they will develop rust. The patina is not of concern and for some it is a mark of pride, but rust can cause long term, sever and permanent damage to the knife. Stainless steel knives still need to be cared for, but they do not require the same attention as described above.
Although it is not definitive, on average high carbon steels can be hardened to higher Rockwell ratings. Harder steels can hold significantly more acute edge angles and therefor can be much sharper and maintain that sharpness for much longer periods. While, softer steels are not capable of holding the same angles and sharpness, the edge they do hold is more durable. However, as you will discover as we go through some of the popular knife steels below many stainless steels can be hardened to just as high Rockwell ratings as their high carbon counterparts.
A couple of quick points about stainless steel before we list of some of the more popular types and their characteristics. High carbon steels if not properly used can tarnish food with a very slight metallic flavour and discoloration. This is not often discernible to most palates, but it is worth noting. This is not something that you should be concerned with in terms of health and really only occurs if the user does not follow a strict knife cleaning process like the one mentioned above. Stainless steel does not suffer from these issues. Stainless steels are also highly recyclable.
It’s really not worth mentioning all the different types of steel that are available, but below we have listed a few of the more popular types that you will see around as you shop for kitchen knives.
|Steel Name||Type||Rockwell (HRC)||Sharpness||Edge Retention|
|White #1 (Shirogami)||High Carbon||65+||♦ ♦ ♦ ♦ ♦||♦ ♦ ♦|
|White #2 (Shirogami)||High Carbon||60-61||♦ ♦ ♦ ♦||♦ ♦ ♦ ♦ ♦|
|Blue #1||High Carbon||65||♦ ♦ ♦ ♦||♦ ♦ ♦ ♦|
|Blue #2||High Carbon||63-65||♦ ♦ ♦ ♦||♦ ♦ ♦ ♦ ♦|
|Blue (Aogami) Super||High Carbon||63-64||♦ ♦ ♦ ♦||♦ ♦ ♦ ♦ ♦|
|VG10||Stainless Steel||60-62||♦ ♦ ♦ ♦||♦ ♦ ♦ ♦|
|VG5||Stainless Steel||60-61||♦ ♦ ♦ ♦||♦ ♦ ♦ ♦|
|VG1||Stainless Steel||58+||♦ ♦ ♦||♦ ♦ ♦ ♦|
|R2/SG2||Stainless Steel||64+||♦ ♦ ♦ ♦||♦ ♦ ♦ ♦|
|ZDP189||Stainless Steel||66-67||♦ ♦ ♦ ♦ ♦||♦ ♦ ♦ ♦ ♦|
|AUS10||Stainless Steel||58-60||♦ ♦ ♦||♦ ♦ ♦ ♦|
|AUS8||Stainless Steel||58-60||♦ ♦||♦ ♦ ♦|
|Silver 3||Stainless Steel||59-61||♦ ♦ ♦ ♦||♦ ♦ ♦ ♦|
That’s it for this post. We use kitchen knives that are constructed out of both high carbon and stainless steels in our kitchen and they are constructed using a variety of different methods. The purpose here is not to define a specific material or construction method and label it as best, but to educate you and help you develop an intuition for what suits you and your needs. In part three of our knife series we will continue to discuss knife construction and delve into the topics of cladding, geometry and handles.