A knife, an extension of a chef’s hand. A sacred unity of man and metal. However, far too often kitchen knives are left dull, dirty and neglected. Then – when it comes time to cut anything – rather than slicing through elegantly, it smashes everything in its path tainting the final product and limiting your potential for high quality dishes. No longer! For here we learn how to sharpen your knife and how to keep it sharp.
Geometry of a Knife Edge
On a macro scale, the cutting edge is just two flat planes meeting together forming a continues sharp edge that we use to cut through food. If we grabbed a microscope and zoomed in, we would see a different picture. On a grain structure level, the metal looks more like a tiny serrated edge. Little “fingers” stick out of the edge and do the cutting. Through use, these fingers become bent, resulting in a dull cutting edge and this is why we hone our knife before use. Over time, these fingers break off. Once enough of them have broken off, the knife is dull and no longer able to be recovered by honing. This is when we must remove material from the blade to achieve a sharp cutting edge again.
Why Use Sharp Knives
Knives can be scary, I get it. I have sliced a large chunk of my thumb off before. However, dull knives are more dangerous than sharp knives. While you may think that a sharp knife will cut you easier, even a dull knife is plenty sharp enough to cut your skin. Dull knives will deflect off of what you are intending to cut and proceed to cut through your flesh with ease. A sharp knife will cut through what you want to cut through (food, not your hand). Keep knives sharp and keep your fingers.
What Steel to Use: Stainless Steel vs. Carbon Steel
First, pay attention to the quality and type of steel.
While you can sharpen a plastic dinner knife to a razor edge, it won’t last long enough to cut through a potato. This same logic applies to steel. While a cheap bargain set of knives can be sharpened to have razor edges, they will dull incredibly fast compared to a high quality blade with proper steel. Seeing as dull knives are a safety risk in the kitchen, it is in your best interest to keep your high quality knives sharp.
When you go to buy knives, you will notice that there are two types of material: stainless steel and carbon steel. No, we are not talking about ceramic, glass or any other fad material. They aren’t worth your attention; just get a set of steel knives and you won’t have to worry about having the right knife for the job. For the vast majority of people, stainless steel knives are going to be the proper choice. Stainless steel allows for better corrosion resistance, keeping the blade sharp after cutting corrosive produce such as onions, lemons and limes. The primary concern for most people in the kitchen is maintaining a sharp edge that doesn’t dull within minutes of finishing cutting tasks.
There is another steel, however. Plain carbon steel is different and offers some very unique advantages compared to stainless steel. Plain carbon steel rusts and corrodes far quicker but allows skilled users to obtain the sharpest edges possible. If you are in a situation where knife sharpness is the main priority, then plain carbon steel is the solution. The most common place where this arises is in sushi cutting. Even sushi masters will sharpen their knifes at least once a day. If you don’t want to spend a few minutes sharpening your knife every time you cook, stick to stainless steel.
Honing a Knife
You know that long steel rod that came with your knife set? The one that your mother-in-law always claims sharpens her knives? Well, it doesn’t sharpen your knife – it hones it. They are different.
Sharpening a knife is the name for the process of removing steel material from the knife to achieve a sharper cutting edge. Honing an edge is when you realign the cutting edge into a uniform strait edge. Honing does not remove any material, it merely aligns the edge that is currently there. Honing a completely dull knife will not result in any noticeable improvement in the performance. This is when sharpening is needed. Conversely, a razor sharp edge will warp and bend during use and be effectively dull without honing.
You should hone your knife before every use and you should sharpen your knife when you notice the honing is no longer reviving your edge back to sharp.
Cutting boards
Proper cutting board choice is key to keeping a sharp edge on your blade and ensuring you’re not spending every weekend on the whetstone. You want a cutting board that is antimicrobial and soft enough on your cutting edge. A glass, ceramic, or stone cutting board is not meant to be used with quality knives. These materials are far too rough on the knife’s edge and will prematurely dull your knife. While some people swear by plastic cutting boards, they are harsher on your knives and will dull them quicker. Wood cutting boards are the best option, not only in performance, but aesthetically. Of note, bamboo cutting boards are an exception here as they are too hard and should not be used. Wood cutting boards are naturally antimicrobial, safe on your edge and easy to clean. You spent your hard-earned money and time on your knives, don’t ruin all that by buying a cheap cutting board.
Cutting Techniques: How to Hold a Knife
First we need to talk about how to hold a knife. Yes, grab the handle, but don’t be afraid to choke up and have your thumb and index finger on the flat of the blade. This will keep your thumb and index finger over the center of gravity of the knife. This gives you more control over the blade, allowing you to make more accurate cuts that are quicker and safer.
Once you have the knife correctly in hand, we need to talk about how to move the knife to cut (yes it matters quite a bit). Push cuts, pull cuts, chopping, and rocking are all important knife skills to master. The main thing to remember is to move the knife towards or away from you while cutting, depending on the cut type. This will allow the knife to do the work and it should effortlessly glide through the food.
How to Sharpen a Knife
Sharpening your own knife shouldn’t be scary. On a macro level, sharpening a knife is just removing material on the edge with the use of a whetstone until sharp. We achieve this by maintaining a constant angle of the knife relative to the face of the whetstone. Repeating this on both sides of the blade while increasing in grit will result in a razor sharp cutting edge. The important thing here is to keep the angle of the blade very, very constant. The thing that separates a novice from a master is consistency in blade angle.
How to Detect a Burr
When you proceed to properly stone one side of your blade, you will develop what is called a burr. This happens from the material being removed and rolling over to the far side of the blade edge. The goal of each sharpening step is to achieve this burr on one side of the knife, then you’ll flip the knife over to repeat the process on the other side.
You will need to learn to feel the burr to see if it has formed or not. There are a few ways to do this, but the best methods are with your finger or your fingernail. Warning, you are going to be touching a blade you are trying sharpen so be smart, go slow and don’t press your finger into the blade. To feel the burr with your fingers, run your finger from the spine of the knife to the edge and feel if you feel an edge pulling against your finger on the cutting edge. You are looking for a slight edge, not a super sharp edge. You can also test to see if you have achieved a burr by using the back side of your nail. Run your nail against the burr and see if you shave a small part of your nail off. This will show if a burr is present. Either way works and it will be down to personal preference on which method you adopt and use regularly.
Grip while Sharpening a Knife
How you grip your knife during sharpening is very important. For the outside edge of the blade (relative to how the blade is when in use), you will want to grip the handle with your dominant hand. Have your thumb on the flat of the blade, index finger along the spine and your remaining fingers around the handle. This will hold the knife at about a 45 degree angle, my preferred sharpening angle. On your non-dominant hand, you’ll place your non-thumb fingers along the blade of the knife, about ¼” above the stone. Be careful as your fingers are close to the cutting edge. As you move down the blade, your non-dominant hand will move to stay above the stone and apply a consistent pressure.
When sharpening the inside edge of the blade, keep the handle in your dominant hand, rotate the blade so that your index finger now rests on the flat of the blade and your thumb runs along the spine of the blade. Your non-dominant hand will now reach over the blade and assume the same position as before with your fingers ¼” above the stone.
Angle when Sharpening a Knife
While the specific angle of your edge will vary from maker to maker, there is a general range that most edges fall into which is 15-25 degrees. The lower the angle, the sharper and more brittle the edge. A 15 degree angle is used in super precise operations like sushi making and sashimi cutting. A larger angle will last longer with the sacrifice of a slightly less sharp edge. Now, if you are like me, you will want to use the lowest angle possible to maximize that edge sharpness. You’ll probably be better off using a slightly higher angle, though. If you’re new to this and try for the lower angle, you will likely roll or snap a 15 degree angle in your first day. The slight added sharpness will be worthless shortly after use. Focus on refining your sharpening skills first – sharpening at at a higher angle to obtain a razor sharp edge when starting out.
When picking an angle to sharpen to, there are many tools and tricks to help. While the change in angle does impact things, it is far more important to keep a consistent angle. Find your angle and stick to it for the knife. If you need to change angles between knives, that’s fine, but don’t change your angle on a blade.
The trick I like to use is to keep the spine of the blade between 1-2 fingers off the stone.
As you move towards the tip of the knife, the geometry will force you to adjust your grip and technique to adequately sharpen. As you move down the blade, you will begin to pick up the wrist of your dominant hand. This will achieve the proper angle throughout the length of the blade. This will take some getting used to, but it will be quick to master and give you the best results.
Pressure when Sharpening
When sharpening your knife, apply 5 pounds of pressure on the blade as you move it away from the edge and 1 pound of pressure on the return stroke. For the outside edge of the blade, this means using 5 pounds of pressure when pushing the blade away from you, and 1 pound of pressure when pulling it back toward you.
For the inside edge, reverse the process: apply 5 pounds of pressure when pulling the blade toward you, and 1 pound of pressure when pushing it away. This technique ensures consistent sharpening while minimizing wear on the blade.
Technique for Sharpening
Through your strokes, you will want to move over then entire length of the stone from corner to corner. This will achieve the most consistent edge product as well as utilize your stone the best, allowing it to last longer. During each stroke, you want to sharpen 3-4 inches of the blade. This will allow you to blend the contours of the edge together, creating a more consistent cutting edge.
What Stones to Use when Sharpening
You are going to want to use 2 stones, a medium grit and a fine grit stone. I recommend a 1,000 grit and a 4,000-6,000 grit stone. This will allow you to achieve a plenty sharp edge that will last longer that a 10,000 grit stone. Also, let’s be real, if you need me to explain how to sharpen a knife – you are not ready for a 10,000 grit stone. You will not see any benefit; instead spend your time practicing your technique at a lower grit and you will find yourself making an edge that can cut a free standing hair in no time.
Whet stones are used because the water in the stone helps create a slurry that better removes material from the edge of the blade. The water also prevents stone and metal dust from becoming air-born, protecting your lungs. There are some dry stone and abrasive plates on the market, however nothing compares to a whet stone.
As for specific stone recommendations, I don’t have any at this point. I recommend you find a local sharpening shop and ask for a good stone for your level and price point. You can also read some stone specific reviews online. Remember that when you’re learning, you won’t be able to utilize the full potential of a high quality stone and there is a potential of premature wear when learning (I turned my first stone into a half pipe after only a few sessions due to lack of technique).
Stone grits
Stone grits are a measure of how aggressive the abrasion in a stone is. The grit relates to the number of particles in a certain area of the stone. Therefore, the lower the number, the larger the particles and the more abrasive the stone is. Think of gravel vs. sand. We start at a lower grit stone to remove more material quickly and obtain the new edge, then move to the higher grit to polish and refine the cutting edge.
In knife sharpening, stone grits between 800-1,500 are considered course, 2,000-4,000 are medium, 4,000-6,000 are fine and 6,000 and up are extra fine. While higher grits can achieve a sharper edge, they require increasingly more skill to properly utilize. Furthermore, they create a more delicate edge that will not last as long as lower grit edges. You may have seen a lot of noise online about insanely high grit stones and how sharp they can get an edge, but – truth be told – the vast majority of people do not need this. In fact, they would probably suffer as the edge would dull faster. An edge finished on a 6,000 grit stone will be the perfect balance of sharp and sturdy for most people.
How to Remove a Burr
While we don’t want to remove the burr at our lower grit, after we finish all the sharpening, removing the burr is essential. Without removing the burr, your blade will not be sharp. This is the final step in the sharpening process. Don’t worry, it’s easy.
There are two methods for removing a burr: on the stone and on a strop. Removing a burr on the stone is more challenging but offers you more control over the grind direction (which sharpening pros are very fond of).
To remove the burr on a stone, hold the knife in your dominant hand, thumb up, with the edge of the blade parallel to the length of the stone. Start on the tip, keeping the blade angle consistent and run the knife over the entire length of the stone. After pushing the blade away from you, flip onto the other edge and repeat pulling the blade towards you. You will get into a rhythm. Repeat until there is no burr remaining.
The second method of removing a burr is more beginner-friendly (and my recommendation if you are just starting out). Take a leather strop and place the edge of the blade on the leather at a slightly higher angle than you were sharpening, ~30 degrees. Push the blade away from the edge only; do not pull towards the edge as you will cut the leather with the edge. Flip the blade over and repeat on the opposite side. Strope the edge on both sides until the burr is gone, approx. 5-6 times per side.
One you have removed the burr on your blade, you are ready to enjoy the absolute joy that is using a sharp knife. Be careful and have fun!
How to Sharpen a Knife at a Glance:
- Soak whet stones for 10-15 minutes or until bubbles stop coming from the stone.
- Place the 1,000 grit stone on a wet towel or stone stand with the short side towards you.
- Spritz stone with water.
- Grab knife in dominant hand with thumb on the flat of the blade, index finger along the spine, and the rest of your fingers on the handle. Placing your non-dominant hand on the flat of the blade, spread out to achieve consistent pressure along the edge. This will sharpen the outside edge of your blade.
- Find your angle by raising the spine of the knife approx. 1-2 fingers off the stone.
- Starting near the heel of the blade, push the knife away from you with 5 lbs. of pressure maintaining a constant angle.
- After a couple strokes, begin to walk your non-dominant hand fingers down the blade as you sharpen further down the blade. Add water to the surface of the stone when none is present.
- As you approach the tip of the blade, raise the wrist of your dominant hand to match the contours of the blade and achieve a consistent edge. Do not change the sharpening angle, just your wrist.
- Keep sharpening the outside of the knife until a burr has formed, approximately 10-15 strokes.
- Flip the knife over. With your dominant hand, place your thumb on the spine of the knife, index finger on the flat of the blade and your remaining fingers wrapped around the handle. Your non-dominant hand will assume a similar position as before with your fingers approx. ¼” above the stone.
- Repeat steps 5-9 on the inside edge of the blade.
- Once both sides have been sharpened, replace stone with 6,000 grit and repeat steps 3-11.
- Once knife has been sharpened, grab your strop to remove the burr.
- Hold the strop short side towards you.
- Place the blade on the strop at a 30 degree angle facing you and push away with less than 5 lbs. of pressure.
- Flip the blade over and pull towards you, going over the entire length of the blade. Do not push the edge into the leather here, it will cut the leather and ruin your strop.
- Repeat until burr is removed.
- Enjoy the blessing of a sharp knife in the kitchen!
Notes:
- Some techniques say to apply more pressure while always pushing the blade away or even when pushing the edge towards the stone. While these can achieve a good end result, I have found that dragging the edge across the stone is more forgiving and will also achieve a great end result. If you want to try this method, feel free (there is nothing wrong with it, just not my preferred method).
- When setting up your work area for sharpening, place your stone in a shallow baking tray to catch all the water and slurry spills. This will make clean up far, far easier.
- To check the sharpness of your blade, grab a sheet of plain printer paper, hold it in your off hand and slice it away from yourself. If the blade is sharpened correctly, it will glide through and leave a clean cut edge. If the blade gets caught in the same spot consistently, it’s an indication that you did not fully sharpen the blade and may need to return to that spot to fully apex the edge.
- Make sure to hone your knife before every use as this will increase the longevity of your blade and provide the safest outcome possible.