On your way to becoming a better cook, there are a few skills you must learn that go beyond actual cooking. One such skill is learning how to sharpen your kitchen knives.

This may not seem like a priority, but it is. First of all, sharp kitchen knives are a lot safer to use than dull knives. Keeping your knives sharp will also save you time when preparing meals and ensure that your food will cook properly. 

Part of the process of learning how to sharpen your knives is understanding how they’re made. This will help you choose the right sharpening tool for the job. Let’s get started.

The Dangers of Dull Knives

Dull knives are a kitchen hazard because they interfere with the way the blade is designed to cut food. When you try to slice or chop with a dull knife, it forces you to overcompensate by applying more pressure and increasing the risk of slippage.

Don’t get me wrong. Sharp knives can be a danger too, especially for children and pets. You can accidentally cut yourself by:

  • trying to catch a falling knife
  • picking up a knife that is soaking in dishwater
  • improperly receiving a knife from someone
  • grabbing a knife that is stored in a drawer
  • not being careful when cutting or slicing
  • pulling the knife toward you instead of away from your body

How To Tell If Your Knife Is Dull

How do knives become dull through use? What happens to the blade edge after repeated use? The answer to both questions can be found in the way metal blade knives are constructed. We will get to that in a minute. But first, let’s look at how to determine the condition of your knife.

There are a few ways to test to see if your knives have become dull through use. They involve running your knife through certain materials or foods to see how it handles. Here are some ‘dull knife tests’ you can try:

Paper test: Grab a piece of printer paper and run your knife through it. Does it glide through like butter or does it hang up? If it doesn’t ‘catch’ on the paper then the knife is probably still pretty sharp.

Magazine test: This is a variation of the paper test. Magazine paper is thin and has a glossy sheen, which makes it hard to ‘catch’ with the knife’s edge. If your knife can slice through this kind of paper (even rolled up) then you’re good-to-go. No, we’re not talking Ginsu knife quality. smile

Shaving test: If you can shave with your knife, it’s sharp enough.

Onion test: Does your knife bite effortlessly into the skin of an onion? If it does, then it probably doesn’t need sharpening.

Overripe tomato test: Too ripe tomatoes are squishy and hard to cut into without making a mess. But a sharp knife should be able to glide through it.

How Knives Grow Dull Through Use

There are many ways a metal knife can become dull through use. It all comes down to the material it is made of, how the edge is shaped, and whether the blade itself can resist chemical attack. 

When a knife’s edge is super sharp it is also mechanically weak. That’s because the degree of sharpness is tied to how much material is left to guard against deformations. This means if the edge hits a hard object it will usually deform into a rounded shape. In the case of a chemical attack, the edge will get eaten away.

Before you get to the task of sharpening your knives, it is important to know the type of material the blade is made of. This will determine the level of difficulty you will have in trying to sharpen it, and what tools are right for the job.

Most non-serrated knives are made of stainless steel, carbon steel, high-carbon stainless steel, zirconia (ceramic), Damascus, or various steel mixtures. 

This chart will help you understand the general benefits and drawbacks of each metal or material type:

Metal Qualities
Stainless Steel
  • Vulnerable to salt, moisture & acid
  • Corrosion-resistant
  • Rust resistant
  • Durable
  • Hard to sharpen
  • Will not take an edge as well as carbon steel
Carbon Steel (carbon added to iron)
  • Strong blade
  • Prone to rust
  • Vulnerable to acids
  • Can show dark stains
  • Holds edge longer than a solid iron blade
High-Carbon Stainless Steel
  • Stain-resistant
  • Holds its edge well
  • Highly functional
  • Durable
  • Strong blade
Ceramic (Zirconia)
  • Extremely sharp
  • Very brittle
  • Lightweight
  • Holds edge for a long time
  • Stain, rust and acid resistant
  • Can chip or shatter easily
  • Sharpening can be a bit tricky
Damascus Steel (Pattern-welded)
  • Dissimilar knife steels welded together
  • The name refers to the process of making the knife
  • Displays uniques patterns on the metal (penetrates through)
  • Extremely expensive
  • The knife manufacturer is a crucial factor related to quality

 

Knife Edge Styles

Every knife you own has been ground to form a certain type of edge. The angle at which the grinding occurs determines the bevel or honed edge of the knife. Most kitchen knives have a bevel edge angle from about 12-35 degrees.

The lower the angle, the sharper the knife. But it will also be less durable and chip more. More durable knives tend to have a larger angle because it can withstand more pressure.

If you take a close look at the blade of your knives, you will see a part of the blade at the very edge that will angle very steeply. This is called the edge angle.  Knife-edge types and styles can vary.

The way the metal or stainless steel has been ground to make the knife sharp is also known as the edge style. Below are a few typical blade edge types for standard kitchen knives.
 

Knife Edges Illustrated

A bevel describes the way the surface of the knife has been ground down to form the cutting edge. Most kitchen knives have a traditional V-edge bevel.

Convex: A cross-section of this type of blade looks a lot like an airplane wing. It gently curves to a point. Therein lies the challenge. This type of edge is harder to sharpen because, after multiple sharpenings, the edges are ground down and take the shape of a V-edge. These can be harder to sharpen with home sharpeners.

Flat Ground (or “V” Edge): This is a standard knife-edge style.

Chisel: This type of edge is the hallmark of most traditional Japanese knives. They are very sharp; with one side ground while the other side remains flat. The edge is small. The flat side has a zero degree angle while the sharpened angle is between 20 and 25 degrees.

Asymmetrical V: Asymmetry refers basically to how the knife’s blade is ground unevenly from side to side. This is very common in Japanese knives. The key is to sharpen the edge bevels as close to matching the asymmetry of the blade itself.

(Compound) Double Bevel: Tends to be stronger and resists rolling because of the support from the second bevel.

Hollow: Mostly found in cheap butcher knives. Edges are concave. They are more susceptible to damage due to the thinness of the blade.

Serrated: (Not illustrated) The cutting edge features a series of small arches that are ground on one side of the knife edge. They are very time consuming to sharpen and a problem to hone. Many professional knife sharpeners will tell you to just buy a new one when your old one wears out.

Choosing The Right Sharpening Angle

When you are ready to start sharpening your knives, the first step is deciding on the sharpening angle. This is probably the easiest step in the process. Keep in mind however that the sharper the edge of the blade, the less durable it will be, and more prone to chipping. You can equate a sharper edge with a narrower angle. When you widen the angle, the result will be a more durable blade edge.

Most factory-made kitchen knife edges have a 10-25 degree bevel angle. So your goal will be to try to match the angle of the original grind.

The easiest approach would be to start at a 20-degree bevel angle. This is within the 17-25 degree range for most kitchen, chefs, boning, and carving knives. Filet, paring, Sushi and almost all Japanese knives will fall within the 12-17 degree range for sharpening.

 How To Calculate Your Angle

illustration of edge anglesWhen discussing knife angles, it is important to understand that the ‘angle’ is only referring to one side of the blade. You have to find the edge angle. You also have to understand that the total cutting angle of your knife is what is called the ‘included angle.’

So, on a V-edge knife, your included angle will be double the edge angle. To determine the cutting angle of your knife, try this: draw an imaginary line through the center of the blade’s cross-section and measure from that point to the outer edge of the primary bevel.

The illustration to the left shows a V-edge blade that has a 12-degree edge angle but the inclusive angle is 24 degrees. If the edge angle was 15 degrees, the inclusive angle would be 30 degrees.

Since not all knives have a V-edge, you will need to identify the type of edge (i.e. chisel or convex) you have, and then apply the right sharpening technique.

The Sharpening Process

There are many approaches you can use to sharpen your kitchen knives. You can sharpen them manually, with electric sharpeners, sharpening systems, or with whetstones.  There are pros and cons to each technique. The main thing to keep in mind is that it will take practice for you to get comfortable and proficient with the process.

Instead of writing out each process, I found several videos that will help any beginner understand the general techniques for sharpening knives manually using whetstones and the Lansky sharpening system. I have included a video that also illustrates the challenges related to sharpening ceramic knives.

Posting these videos are for instructional purposes only. It is not meant as an endorsement of any product and I do not receive any type of compensation for the products shown in these videos.

Manual Sharpening Technique by Outdoors55

Tools: Norton Sharpening Stones, Knives Plus Strop Block, Spyderco Pacific Salt

 

Lansky Controlled Angle Deluxe Diamond Sharpening System by Charlie DIYte

Tools: Lansky Super C Clamp

 

Sharpening A Ceramic Knife by Doug Holser

Tools: Diamond abrasive belts in two grits:180 and 1500

 

A Few Words About Honing (or Steeling) Your Knife

Up to this point, I haven’t mentioned sharpening or honing steel. That’s because technically honing steel is not meant to be a knife sharpener. It is more of a maintenance tool that’s designed to keep the edge of the knife straight. The more you use your knife the more it ‘bends’ as microscopic fibers bend over and dull the edge. When you regularly ‘steel’ your knife the process will straighten the fibers back out. It is a way to keep the knife-edge sharp until you sharpen it again.

 


Master Blade Smith Bob Kramer via Good Housekeeping

Knife Sharpening Options

When deciding on how to sharpen your kitchen knives, you have several options:

  • sharpen them manually
  • use an electric knife sharpener
  • hire a professional

Electric knife sharpeners are certainly easy to use, but if you don’t carefully monitor what you’re doing, you may end up removing more metal than you need to. Although the focus is on kitchen knives, some can also sharpen scissors, ceramic knives, hunting knives, and meat cleavers.

Manual sharpeners, on the other hand, requires some skill, but you’re less likely to thin out the blade too much. There are also many companies that specialize in knife sharpening services if you don’t want to tackle this yourself.

No matter what option you choose, honing and sharpening your knives on a regular basis will protect your investment and make cooking a more enjoyable experience.