The Science of Knife Sharpening
A sharp knife is a chef’s best friend. Not only are sharp knives easier to use, they’re safer as well. But even the best blades will dull with use if not properly maintained. Whether or not you’ve invested in high-quality knives, regular maintenance (with the right tool) makes knife sharpening fast and foolproof—extending the life of your knives and equipping you to prep like a pro in your home kitchen.
What is a Dull Knife?
A sharp knife is two planes forming a bevel with a microscopically thin edge. Regular use puts enormous pressure on this edge, causing it to bend or roll to the side, becoming dull. Although thin, the edge is still very hard and will not simply flatten like a lump of clay. It needs to be pressed back into shape to realign the edge.
If left unchecked, the bend will become worse and eventually fold over, flatten, or even break. Eventually the damage will be so severe, the only remedy is to remove the metal to restore the correct bevel and create a new edge. Edge reshaping is traditionally done with a hardened steel rod, also known as chef’s steel, but considerable skill is required and improper use can further dull the blade. No matter their composition or blade angles, all metal knives benefit from regular steeling or polishing to keep the hard blade aligned so it doesn’t break. This is especially critical with harder steels, such as those found in some high-end Japanese knives, as they tend to be more brittle and can break while honing if allowed to become significantly bent.
A Quick Look at Knife Characteristics
The composition and characteristics of steel for knife blades is a broad and complex subject, but two of the more basic characteristics are hardness and toughness. Hardness is the resistance of a metal to changing shape or deforming. A hard steel can be sharpened to a very keen edge. Seems like a great choice for a knife blade, but it comes with a price—hard metals tend to be brittle. Toughness is the ability of a metal to absorb a blow without fracturing. Hardness and toughness don’t usually come together, you can have one or the other, but not both. Much of the secret in great knife making is balancing these two characteristics either with exotic specialty metals or by physically sandwiching different materials together.
What is the best angle for regular honing and sharpening? Opinions vary, but the range can be from 11/12 degrees for the sharpest filleting knives to 20/21 degrees for a blade that will hold up better to rough chopping. The larger the blade angle, the more durable the blade will be, although perhaps not quite as sharp. A good knife sharpening system needs to accommodate a variety of blade angles for both sharpening and honing.
Traditional Sharpening Methods
Traditional knife sharpening techniques of grinding with an abrasive stone, industrial diamonds, or even sandpaper can be effective, but are more likely to damage knives or over-sharpen them to the point of a “scary sharp” edge inappropriate for most kitchen knives. Freehand sharpening is difficult to perform precisely and takes a lot of practice. Coarse abrasives remove metal quickly but leave a rough edge that requires time consuming refining.
A New Approach to Knife Sharpening
4 Functions. 1 Sharpener. Engineered in Austria by a master knife maker, and inspired by the science and materials used in the metal machining industry, Brod & Taylor knife sharpeners use a completely different sharpening technique. Two ultra-hardened, tungsten carbide sharpeners are fashioned in a specialized shape and mounted on spring-action bars. This patented system creates four distinctly different sharpeners in one, with the sharpening function determined by the angle of the knife as it is pulled through.
Hone. With the knife tip up - realign a rolled edge without removing metal. Great for daily maintenance.
Sharpen. With the knife tip down - quickly restore the correct bevel shape to very dull or damaged knives.
Serrated. For serrated knives, pull the knife through at an angle to hone and sharpen each serration.
Polish. Create a super-smooth and sharp edge by widening the angle and polishing back and forth.
Easy Knife Maintenance
Honing knives each time before you use them only takes a few seconds. We recommend 6–8 pulls through the sharpener (tip up). If you need that extra degree of sharpness, polish the edge with a few strokes back and forth. Let the sharp edge glide across the smooth flat surfaces of the sharpener with no more downward pressure than the weight of the knife. Wipe the blade clean with a damp cloth. After using your knives, wash promptly, wipe clean, and store carefully. If storing knives in a drawer, cover them with a blade protector.
How Does it Work?
The best way to sharpen kitchen knives depends on the type of blade you are sharpening and how you will use it. The Brod & Taylor sharpener automatically adjusts the bevel angle to accommodate different types of knives and your various sharpening needs. Go from 12 degrees for the sharpest filleting knives to 20 degrees for a knife intended for rough chopping. Here’s what you need to know about knife sharpening angles:
- The larger the blade angle, the more durable the blade will be, although perhaps not quite as sharp.
- Use light pressure to cut a more delicate, but sharper 12 degree angle bevel.
- Use more pressure to fully compress the springs and cut at a sturdy 20 degree angle.
- Always hone the knife with at least as much pressure as was used to cut the bevel.
- If in doubt, use a bit less pressure when sharpening a bevel, and a little more when honing.
- More pressure when honing will never damage the blade, but if too little pressure is used, the honing may not reach the very tip of the edge.
- In all cases, polishing with the sharpener bars spread wide will burnish the very edge.
What does the Tungsten Carbide Do?
The best knife sharpening tool achieves a balance of sharpness, durability, and is fast and easy enough to encourage regular maintenance. A good knife sharpening system also needs to accommodate a variety of blade angles for both sharpening and honing. Both of our knife sharpeners do just that thanks to their precision machined tungsten carbide edges, shown in this cross-section.
The “leading edge” of the tungsten-carbide is ground to a sharp corner, which sharpens by cutting the correct bevel on a metal blade with a few quick strokes. This coarse sharpening is done only rarely, when the edge is too dull to restore by honing alone.
The “trailing edge” is ground with a small, smooth bevel. The beveled corner pushes, re-aligns and smooths the edge into shape. It only takes seconds to realign a blade and maintain a sharp knife. No special skills are required.
The honing process (drawing the knife through the sharpener with the tip up) works just like a well-controlled chef’s steel: proper angle and pressure are maintained by the spring-action bars. The flat surface of the carbide is finished to a mirror surface, allowing very fine edges of knives to be polished to ultimate sharpness.
Polishing involves holding the sharpener's bars spread wide while the sharp blade is guided back and forth across the flat surfaces of the sharpeners without pressure. This allows the metal at the extreme edge of the blade to be polished—or burnished—and become extremely sharp.
How to Sharpen a Serrated Knife
Knife manufacturers devote a lot of time and expertise to creating precisely engineered serrations that will easily slice through thick-skinned or crusty foods. Sharpeners that remove metal eventually change the shape of the edge, eroding the points, flattening the curves, or grinding the flat side of the knife. True non-metal-removing honing is the best way to maintain these edges at home because it preserves the shape of the serrations.
Almost all serrated knives have a blade that is beveled on one side and flat on the other. For most, the beveled side is on the right as you’re holding the knife in the cutting position (therefore the left side is flat). This one-sided anatomy makes serrated knives tricky to sharpen. In order to avoid changing or damaging the original shape of the blade, they should only be sharpened on the beveled side, while the flat side is left alone.
If your knife is serrated on the right side, your hand should first move right while the tip of the blade moves left when sharpening. Pull the knife smoothly through the sharpener. The knife blade should touch only one side of the carbide sharpeners (on the side with the serrations). Rotate the blade in the opposite direction if your knife has serrations on the left side.
Whether you opt for the gentle scalloped edge or prefer the way the pointed shape of a classic serration glides through tough crusts, regular honing will keep these beautifully-designed edges at their best. The spring-action, Austrian-made honing surface in our sharpeners hugs the entire shape of each serration, while pulling the knife through at an angle ensures that the honing surface only touches the beveled side of the knife.