How do Knives Become Dull?
Besides learning to sharpen, the best way to ensure your knives stay sharp is to avoid unnecessarily dulling them. Knives become dull in a number of ways, often due to misuse. For kitchen knives the most common reasons for dullness are: cutting on surfaces that are harder than the knife edge (ceramic plates, glass dishes, or marble/granite counter tops) and storing the knife loose in a utensils drawer where the edge can bump into other utensils causing nicks and damage. Most dulling that occurs is a result of the very fine edge of the knife being rolled or folded over. If treated properly a good quality sharp knife may not require sharpening (with abrasives) for weeks, or even months depending on usage. We made the following video to explain dulling in more detail.
Checking for Dullness and Sharpness
There are a few easy ways to test whether your knife is sharp or not. If the knife in question is one you use regularly you will notice when cutting performance begins to drop off, this is a very good indicator of dullness. To get a rough idea of the state of the edge, view the cutting edge under a bright light. A sharp knife’s edge will reflect no light because the two sides of the knife come to a razor fine edge. Conversely a dull knife’s edge will appear shiny because the two sides of the knife form a blunt rounded edge which reflects light. Another quick indicator is dragging a finger or thumb lightly across (as in perpendicular to the blade), a sharp edge feels grippy whereas a dull edge feels smooth. You may also notice a dry ringing sound when you drag across the edge of a very sharp knife. An easy cutting test can be performed using paper. Hold a piece of paper in one hand between thumb and index finger and lightly draw the knife across the edge of the paper, it should bite in and slice through the paper easily. If it slides off the edge of the paper or tears it instead, the knife is dull. In the video below, we demonstrate the concepts and tests mentioned above.
All knives need maintenance occasionally; frequency will depend on the quality of the knife as well as its usage and treatment. There are two types of edge maintenance: sharpening, and straightening. Of the two, straightening is necessary more often, particularly on kitchen knives because the shallower angle at their cutting edges allows the steel in the edge to bend over to the side. Straightening is done with a honing steel. We highly recommend kitchen knife users have both a steel for regular edge straightening and an abrasive sharpening tool for occasional sharpening. Outdoor knife users should have a small abrasive sharpening tool for touch ups in the field and a main sharpening tool (such as a water stone or jig type sharpener described below) for thorough sharpening at home.
What is a “honing steel”?
A traditional “honing steel” is a very hard metal rod with a handle. During normal knife use, the delicate cutting edge can get deformed or “rolled over.” The metal rod on a traditional steeling tool is harder than the steel in knife blades and its primary job is to straighten up a rolled-over edge rather than abrading it to make the knife feel sharp again. For knives that are truly dull, not just deformed, a traditional honing steel will have no effect. However, honing steels are now made in many configurations besides the traditional smooth models: some have abrasive qualities as well, either file-like ridges along the steel rod or diamond coatings, some are even ceramic. These more aggressive types of steels not only straighten the edge but also remove a small amount of metal from it. Depending on its aggressiveness, you may not need a separate tool for sharpening. When you notice your knife’s cutting performance has decreased, use a honing steel to touch up the edge. “Steeling” only takes a few seconds and is done frequently, every day or every few days as needed.
To use a honing steel place its tip on a cutting board and hold it with the handle in the 12 o’clock position. Now bring the knife against the steel at approximately a 10-15 degree angle. Pull the knife down and across the steel from the heel to the tip while maintaining the angle. Next switch sides and repeat the process on the other edge of the knife. Repeat on each side of the edge, 5-10 times. For the first few strokes on each side use about 5 lbs (approximately 2.5 kg) of pressure (get a feel for this by holding the knife by the handle and push on a kitchen scale with the side of the blade until it reads 5 lbs.) The last few strokes should use successively lighter pressure. It is important to steel using alternating strokes. A knife can not be steeled indefinitely, eventually it will require true sharpening. If the knife is still dull after 10 passes per side on the honing steel, it will require sharpening (metal removal).
A steel is essential to proper maintenance for kitchen knives. There is no reason to pay more than $25 for a honing steel with many available for under $20. Even models which incorporate ceramic or diamond abrasive can be had for around $25-$35 from a name brand such as DMT. A honing steel will last you a lifetime.
Note: Knives with very hard edges (HRC 63 or so) may not be good candidates for steeling due to the chance of edge chipping (a steel places a lot of pressure against a very small part of the edge).
How can I Sharpen my Knife?
If a knife exhibits that shiny edge we mention above, and steeling isn’t the cure, the knife is dull and needs sharpening. There are many tools to sharpen knives. They all work on the same basic principal, metal is removed from each side of the cutting edge until the two sides meet at a clean, sharp edge. Regardless of sharpening tool it is key to keep the sharpening angle consistent, some tools do this for you. Below we discuss a few common types of sharpening tools.
Sharpening takes longer than steeling: depending on the method and degree of dullness, between 2-10 min per knife, but is not necessary very often if the knife is treated with care and steeled frequently. There are three variations on abrasive sharpening tools we recommend depending on what type of a user you are. The tools mentioned below should be available from kitchen or knife stores or specialty suppliers either locally or online. We recommend against using any electric sharpening tools or carbide pull through sharpeners. If you feel uncomfortable sharpening your own knives please seek out a reputable professional sharpening service.
V-style sharpeners (not to be confused with pull through sharpeners) are very simple to use and and yield similar results to water stones. For those who are intimidated by the idea of sharpening, this is the tool for you. Almost anyone can use one of these successfully after watching a good instructional video. V-style sharpeners make the user’s life easy by holding the sharpening “stones” at the correct angle. All the user has to do is hold the knife perpendicular to the base of the sharpener (which is quite easy to do).
A typical V-Sharpener is comprised of two or more abrasive rods and a base of some sort. The base has two angled holes in its surface for the rods to plug in to. Each hole is between 10-20 degrees from vertical (depending on the manufacturer) and set in mirror opposition to the other. When inserted in the holes the rods form the “V” shape that gives this family of sharpeners its name. Some of these sharpeners also have a second set of holes at a different angle, pick the angle which is closest to the angle of your knife edge without being less. The most common type of abrasive rods are coarse and fine ceramic, in some kits the coarse ceramic rods are replaced by diamond rods. A couple of popular models are the Spyderco “sharpmaker” (quality sharpener but on the expensive side) and Lansky’s “Turn box” kits (a very affordable option). All V-style sharpeners work on the same basic principals; Watch our video which demonstrates their use below.
- Assemble the sharpener with the coarse rods
- Hold the knife perpendicular to the base with the cutting edge down
- Place the heel of the knife against the top of either rod
- Still holding the knife perpendicular, slide it down the rod and pull it towards yourself so the whole cutting edge has contacted the rod by the time your stroke ends at the base.
- Repeat step 4 on the other rod to sharpen the other side of the cutting edge.
- Continue to do 10 alternating strokes per side
- check the edge of the knife to see if it feels sharp and reflects no light. If it seems sharp move on to step 8, if not repeat step 6 until sharp.
- Now switch out the coarse rods for the fine ones
- Use the same method as with the coarse rods to refine the edge; approximately 10 alternating strokes
- The knife should now be sharp, slicing paper with ease. If not repeat the last step or switch back to the coarse rods if necessary
For the technical user who is willing to put in some time to learn a new skill we recommend water stones as the best way to get a super fine edge. We use water stones to do the final sharpening of each knife that we make. Ideally a stone in the 800-1000 grit range is used to do the main sharpening and then a 3000-6000 grit stone is used for the final passes to bring the edge to a mirror finish. Combination stones with 800-1000 grit on one side and 4000-6000 on the other are available. Getting the angle right and learning to hold the knife steady at that angle is important to getting good results with water stones. It is simply a matter of practice but good results can be achieved relatively quickly. When buying water stones, buy name brand from a reputable source such as Lee Valley Tools. “King” stones are a good example of a quality Japanese made stone that is also very affordable. A combo stone will be your best bet to keep the cost down. For the average user a quality stone will last a life time.
In the following video we cover a lot of subtle detail and the reasons why we do what we do. Below the video we also provide the written steps. You will probably find it helpful to look through both.
- Wet the stone(s) with clean water according to the manufacturer’s instructions. Ours are in water full time.
- Remove coarser stone from water and place on a stable surface. Orient the stone with one of the ends facing you. You may need to elevate a thin stone to create finger clearance above the working surface. Splash water on occasionally during use to keep the stone’s surface wet.
- Place the knife blade flat across the narrow dimension of the stone.
- Observe the gap between the cutting edge and the stone’s surface. Now, (pivoting the knife on the cutting edge) raise the spine of the knife until the gap disappears and cutting edge seems to mate seamlessly to the stone’s surface. Note how high the spine of the knife is above the stone at this point. This is the angle you want to sharpen at. Check this angle again as needed throughout the sharpening process. With practice you will have to do this less and less.
- Start the sharpening stroke with the cutting edge facing you, holding the knife in your dominant hand with the fingertips of your other hand on the flat of the blade. Regardless which side of the knife your are sharpening, all your strokes will involve pulling the edge over the stone rather than pushing it.
- Place the tip of the knife near the dominant-hand corner of the stone closest to you.
- Holding the knife at the angle we determined earlier slide it down and across the stone(diagonally away from yourself) in a smooth motion with medium pressure. The entire length of the cutting edge should contact the stone during each stroke.
- Repeat step seven 10-15 times (rechecking the angle as needed)
- Now it is time to sharpen the other side of the cutting edge.
- Start the stroke with the cutting edge facing away from you and the tip in the dominant-hand corner furthest from you.
- Using the same angle (use the same trick to get the angle right) pull the knife towards you and diagonally across the stone mirroring the motion from the first side.
- Repeat step eleven 10-15 times.
- Next do a single stroke on each side starting with the first side
- Now draw the knife’s edge lightly through a piece of wood 2 or 3 times. This step knocks off any weak burr or wire edge that has formed. This is very important for achieving the sharpest edge possible
- Next do 3-5 single strokes per side, alternating sides with each stroke.
- Check the blade for sharpness using the light test (described above), you should see no reflection from the edge.
- If the knife passes the light test move to the fine stone. If not repeat step 15 until it passes.
- Prepare your fine stone with water and orient in the same manner.
- Follow steps 3-15 on the this stone.
- Repeat steps 14 and 15 a second time.
- After the fine stone the knife should slice paper effortlessly as described in the “checking sharpness section” above.
Jig sharpeners hold the knife securely for you and guide a sharpening stone over the blade at your angle of choice. When used correctly with the right grits they will yield results very similar to a water stone, without the difficulty of learning to hold the knife at a steady angle. Most users will be able to use this type of sharpener successfully after watching the manufacturer’s instructional video and a few minutes of practice. Many companies make similar systems which work on the same basic principals Lansky, Gatco and DMT each offer a number of jig type sharpening systems. These jig sharpeners commonly come with a set of stones, usually 3 or more. Most have at least coarse, medium and fine stones. If you choose to buy a jig sharpener look for one that has fine stone of 1000 grit or higher. Each jig sharpener is a little different in its design and operation. The key to success with any of them is to follow the instructions closely and look for instructional videos on the manufacturer’s website and youtube to ensure you are using it correctly. As with all tools it will take some practice (perhaps not on your best knife) to get the best results. We have prepared our own tutorial on using one of these systems: the Gatco kit:
Still not Sharp?
Have you watched videos, read instructions and learned a sharpening technique but your knife just isn’t getting sharp? The most common reason for this is that the sharpening angle is wrong. Imagine each side of your knife’s cutting edge as a plane. On the majority of knives, these two planes are each tilted at around 10-15 degrees to make an overall (inclusive) edge angle of 20-30 degrees. When you sharpen, you want to sharpen at the same angle as those existing planes, to make them meet at a sharp edge. If your knife has an edge angle of 25 degrees you need to resharpen it at 25 degrees. If you are sharpening at only 20 degrees you are effectively not sharpening the knife’s edge. You would eventually change the knife’s edge from 25 to 20 degrees at which point it would be sharp. This is an unnecessary removal of material and may affect the performance of the knife. Sharpening the same knife at 25 degrees you will quickly achieve a sharp edge because your sharpening efforts are cleaning up the existing planes, instead of reshaping them to a different angle. The two planes will quickly be meeting cleanly again. The best way to check if your sharpening angle is correct is shade each side of the cutting edge with a permanent marker. Then proceed to a few strokes of sharpening per side. Check each edge to see where the shading has worn off. If the shading is gone above the cutting edge but still there at the cutting edge, the angle is too shallow. If most of the shading remains, but is worn off right at the cutting edge, the angle is a little steep. Ideally, the shading should wear off evenly right to the cutting edge.