Carbon steel has always been used for forging knives. But what is carbon steel, how does carbon steel differ from stainless steel, what are the properties and the advantages and disadvantages of both types of steel? These and other questions will be clarified in this article.
What is carbon steel?
Carbon steel is (rusting) steel that consists of iron and carbon. Depending on the mixing ratio, the proportion of iron is between 98-99% and the proportion of carbon between 1-2%. Since pure iron would be too soft, carbon is used in addition so that the steel reaches a certain hardness.
What is stainless steel?
Stainless steel, i.e. stainless steel, contains iron and carbon, as well as chromium and other elements. The content of iron in stainless steel is about 70-88%. The content of chrome is about 10-14%.
For steel to be considered stainless, the chromium content must be at least 10.5%. The addition of chrome "refines" the steel, makes it shiny and makes it more resistant to rust. In stainless steel knives other elements such as nickel, molybdenum or vanadium are often added to improve the properties of the steel.
Differences between carbon & stainless steel knives
The differences become clear after the first cutting. Chef's knives made of carbon steel react with the acids contained in food after the first cut.
Cutting acidic foods such as tomatoes, lemons, onions etc. once allows the steel to react and immediately discolours parts of the knife dark.
This discoloration is caused by oxidation and is called patina. This patina is normal and unavoidable with carbon steel knives. Even if the patina looks unattractive and dirty to some people, it is still useful because it is a protective layer for the steel. It gives the knife character and tells its own story over time.
If the carbon knife is new and has not yet formed a patina, it reacts strongly with all acids. If the knife has been in use for some time and has formed the protective patina, the carbon steel does not react as quickly with the food.
Because carbon steel is unalloyed, it quickly starts to rust when exposed to moisture. To illustrate how quickly carbon steel rusts, a single washing cycle in the dishwasher is sufficient. Even high humidity causes carbon steel to rust. Therefore, carbon knives should always be dried after use and rubbed with oil if stored for a long time.
If rust still forms on the blade, it can be removed quite easily. Especially easy to remove is superficial rust, the so-called rust film.
Stainless steel knives on the other hand are very inert, i.e. they shine just as well after years of daily use as on the first day. They do not discolour with acidic foods.
Although stainless steel knives can start to rust if handled incorrectly, rust on stainless steel is much harder to form, so for simplicity's sake they are called stainless.
The disadvantage of stainless steel knives is that they are usually not as sharp as carbon knives. They also have a lower cutting durability due to their lower hardness. Because of the carbides found in stainless steel, these knives cannot be sharpened as easily.
Advantages of carbon steel
Sharpness and cutting behaviour are the most important properties of knives. Here carbon knives are way ahead because they are much sharper than stainless steel knives. High-quality stainless steel knives can also achieve a similar sharpness as carbon knives, but are usually much more expensive. If you attach great importance to sharpness, there is no getting around carbon steel.
The long cutting life is another major advantage of carbon steel. If stainless steel knives and carbon knives are equally hard, stainless steel knives have a longer cutting life due to the hard chrome carbides.
However, since most stainless steel knives have a Rockwell hardness between 55-59 HRC and carbon knives have a hardness of 60 HRC and above, carbon knives are generally much harder than stainless steel knives. Due to the significantly higher hardness, the blade of carbon knives does not dull as quickly and therefore remains sharp longer.
Since chromium is added to stainless steel knives, some of the chromium becomes chromium carbide. Carbides are very hard and make the grinding process noticeably more difficult.
Carbon knives, on the other hand, consist only of iron and carbon, which is why they do not have any hard carbides that make the grinding process more difficult. Therefore knives can be sharpened on carbon steel very easily.
Of course there are many factors that influence the price of knives. In general, carbon steel is cheaper to produce than stainless steel. A good carbon chef's knife can cost between 60-120 Dollars and will cut much better than a similarly priced stainless steel chef's knife.
Disadvantages of carbon steel
The biggest disadvantage is probably that carbon steel quickly begins to rust. If handled correctly, rust is not a problem. If carbon knives remain moist after use and are not dried promptly, rust spots will appear very quickly.
Although superficial rust can be removed very quickly and easily, it should be avoided as much as possible, especially with cooking knives that come into contact with food.
As mentioned above, carbon steel will tarnish and develop a patina that is unavoidable. Although this patina has many advantages, for example it protects better against rust, it is not so nice to look at for some people, because they associate a dirty blade with the patina.
If you attach great importance to the appearance and want your knives to always look nice and shiny, you should get stainless steel knives.
What is a patina?
A patina is basically a type of black rust. However this black rust (Fe3O4, magnetite), unlike red rust (Fe2O3, hematite) is not harmful and even protects the blade from the harmful red rust. Unprotected carbon steel is very reactive and reacts quickly to external influences such as water, heat or acids.
In order to take away the steel's ability to react, the patina can either be allowed to develop over a long period of time or the process can be accelerated by creating an artificial patina.
In Western countries the patina is considered positive because it protects the knives and each carbon steel knife develops an individually distinctive patina over time. Each knife thus becomes unique because of the different patina and is different from other knives. In Japanese kitchens the patina is rather undesirable, as it is associated with dirt and impurity.
Is carbon steel safe?
Compared to other metals, carbon steel is relatively reactive. Therefore, the question is often asked whether carbon steel is safe in the kitchen. The short answer is:
Yes, carbon steel is a safe material for knives. However, pans made of carbon steel should be used less frequently.
Each material has different advantages and disadvantages. The big disadvantage of carbon steel is the aforementioned reactivity. This reactivity causes iron ions to be released into the food, which are then absorbed by the body. Iron ions are unproblematic for most people in small quantities, but can become a problem in the long term if used too often.
Carbon knives have less contact with food, which is why fewer iron ions get into the food. Therefore, kitchen knives made of carbon steel can easily be used regularly.
Carbon steel pans have significantly more and longer contact with food. This means that significantly more iron ions get into the food. If iron pans are used too often for cooking, this can become a problem for healthy people in the long run. Therefore I would use either stainless steel pans and pots or a pan with a non-stick coating for cooking.
Which is better? Carbon or stainless steel?
As so often in life, there is no clear answer to this question. You have to decide for yourself what you value in knives and what you value more.
If sharpness and edge retention are particularly important, then carbon steel is the right choice.
If you want easy-care knives that always shine and a good sharpness of cut is sufficient, you should go for stainless steel knives.
So the question should not be which material is better, but which material is more suitable for you.
Proper care of carbon knives
The maintenance of carbon steel knives is relatively simple. Chef's knives should be cleaned after use either with pure water or, if necessary, with a little washing-up liquid. Then wipe with a dry cloth and place it in the knife block, the knife rack or the drawer.
Outdoor knives should also be dried immediately after getting wet. A dry abrasive surface, such as your own clothing, is sufficient for this purpose.
Outdoor knives are more likely to rust due to external influences, so rust cannot always be avoided. If rust has formed, it should be removed as soon as possible, as long as it is only superficial.
For whom is carbon steel suitable?
Carbon steel is particularly suitable for knife lovers who want unconditional sharpness and always take good care of their knives. In addition, the knives are also suitable for people who are lazy about sharpening, but who always take good care of their knives.
Those who are interested in traditional Japanese knives will also not be able to avoid knives made of carbon steel.
For whom is stainless steel better suited?
Those who see their knives simply as a cutting tool and do not attach much importance to extreme sharpness, do not want to dry the knives immediately after use and for whom a clean look is more important than sharpness, should rather choose stainless steel knives.
Stainless steel knives are also preferable in very humid environments where the knives are constantly exposed to moisture.
Carbon steel has its advantages and disadvantages and will always be preferred by certain people and avoided by others. In the end it depends on what you use the knives for and which characteristics are individually more important.