A very common question among home cooks, amateurs and even professional chefs is: "which knives stay sharp the longest?". After all, having a knife that dulls quickly or that requires frequent sharpening involves some work and can be tedious, especially if you're looking for an easy-to-maintain solution for your kitchen.
We understand that most people don't want to spend extra effort taking care of their blades or figuring out how to, so in this article we'll cover (1) what makes a knife sharp in the first place, and (2) what type of steel allows a knife to retain its edge for long.
What Makes A Knife Sharp
This is the million dollar question that can be confusing with so much information around. Some say it's the steel and others say it's the shape, but it all boils down to physics.
What really makes a knife sharp is its blade angle. Simply put, the acuter (i.e. lower) the angle, the thinner and sharper the edge will be. This happens because a thin blade means that more force will be exerted over a smaller area, allowing the knife to cut cleanly through.
Many sources may claim that there are other factors at play, but the blade angle is the true variable of sharpness and the one you should be looking for when shopping for a knife. It makes sense, right?
A sharp knife angle is 13° to 17°, and a standard knife angle is 18° to 22°.
Which Knife Holds Its Edge The Longest
The edge retention of a knife is fully determined by its blade steel—the harder it is the longer it will stay sharp, and vice versa. Hardness matters because a softer blade will deform more easily, leading to its edge flattening over time.
Think of a rock versus a bamboo. The rock won't change its shape so easily as it's used, but a bamboo will quickly bend and deform if enough pressure is applied.
The scale for hardness is HRC (Hardness Rockwell C). Standard knives have an HRC of 51-55, professional cooks typically look for HRC 56+, and very hard steels (typically Japanese) hover around 58+.
If we want to get into the science behind hardness, it's controlled by adding carbon to the steel. Higher carbon content leads to increased hardness.
If you're looking for a knife with good edge retention, and a sharp blade that makes cutting through food easier, we recommend the Kizaru Kanji 3-Set. It's a luxury set of kitchen knives, backed by thorough research. It may be a biased recommendation, but it's also a good one!
With that said, whatever knife you choose to get, make sure to remember that blade angle and material matters a lot—so keep them in mind when shopping around!