Honing is the finishing process where the burrs formed from the sharpening process are removed and a sharpened knife is finished to a fine edge. Honing is also used to maintain the edge in between sharpening. Honing does not actually sharpen a knife. Instead, honing straightens, cleans, and polishes the edge of an already sharp knife. Knife edges are very delicate. After just a few uses the blade edge can begin to actually fold back on itself at a microscopic level. Honing for blade maintenance straightens out the edge and prevents premature dulling of the knife. There are many techniques for honing a blade, including the use of strops, felt wheels, oil stones, and ceramic and steel rods.
The oldest method for honing a blade is the use of a high-grit (1000 grit or higher) oilstone. To hone a blade on an oilstone make sure the stone is properly oiled and establish the proper angle to match the bevel of the edge. Then draw the blade towards the edge as if slicing a decal off of the surface of the stone. Switch sides of the blade with each stroke to avoid building up any burrs.
Honing steels are a common accessory to kitchen knife sets. Steels are rods used to sharpen longer blades such as a French Chef's Knife. Kitchen knives are most often manufactured from stainless steel to prevent rust. The problem is that stainless steel is relatively soft, and the blade will dull easily. As you use a stainless steel blade the edge actually begins to fold over. A steel straightens the edge to give a sharper cutting surface. Using a steel is a skill that can take hours of practice to get right, primarily because the angle of the blade against the steel must be established manually.
To use a steel, hold it by the handle with a grip that places your thumb on the top with the rod hanging down. Place the tip of the rod on a cutting board or other suitable surface. Position the blade you are sharpening at a 22.5 angle using the halving method described in the article titled "Sharpening with a Whetstone or Diamond Plate".
Starting with the back of the blade (the part closest to the handle) at the top of the steel, draw the blade towards you while moving it down the steel. Use ten strokes on the steel on one side of the blade, then 10 more on the other side. When you are done honing the blade on the steel, rinse and wipe down the blade and the steel to remove any metal filings or dust.
Felt wheels attached to a bench grinder are a fantastic way to quickly put a fine-edge polish on a blade. When using a felt wheel on a grinder, make sure to reverse the spin on the grinder, or turn the grinder around so that the top of the felt is spinning away from you. If you have the felt wheel spinning towards you, the wheel could easily grab the knife and throw it at you, potentially causing a serious injury. Remember to wear personal protective equipment like gloves, safety glasses, and a respirator.
Apply a honing compound to the wheel. Hold the knife flat and level with the blade edge facing away from you. Where you apply the knife to the felt wheel will affect the bevel angle you get. The angle of the bevel you are polishing is going to be identical to the radial angle from the center point of the wheel. The illustration to the left shows approximately where the 22.5- and 15-degree angles are on the wheel. Apply the blade to the wheel at the appropriate point for the angle of your bevel.
It doesn't take long to hone a knife is this fashion, only 20 seconds or so per side. If you continue to hone the blade any longer than that it will begin to heat up. Heating up a blade will anneal it and soften the metal. If you are unable to finish a blade in thirty seconds or less the blade needs to be sharpened on a stone and then returned to the felt. As you hone blades the compound on the wheel will turn black from the steel dust. You will need to periodically recharge the wheel with more honing compound. To remove the compound, apply a wooden block to the wheel to scrape it off of the felt.
Leather and canvas strops are a well known method for sharpening razors and other hand tools. They also do a fantastic job of giving knives a slippery sharp edge, and should be a part of the regular maintenance of polished blades. Strops can come as just leather or just canvas, but they are also available as leather on one side and canvas on the other. Strops work the best on blades that are flat on one side (like a scandi grind or chisel grind) like straight razors and Asian-style, single-bevel knives. Having a flat or scandi grind allows you to place the blade flat on the strop. Because the strop is made from leather, it will flex with the pressure of the blade. This makes it incredibly difficult to strop a multi-bevel edge.
Hanging strops have one end attached to a wall or other sturdy object. Most professionals recommend "warming up the blade" on canvas first before proceeding to leather. In my experience this is not necessary; you can go straight to leather and forego the canvas. Care for canvas strops is different than leather strops.
There are four main pastes used on strops. Green paste is the coarsest paste with the largest abrasive particle size. Red is the next step down and has abrasive particles averaging about 3 microns in size. Yellow paste is a conditioner and does not have any appreciable polishing qualities. This paste is for use in cleaning and conditioning your strop. White paste is a very fine-edge polish that is for use on linen canvas strops. Once you use a particular grit abrasive on a strop, you should dedicate that strop to use with only that paste. The microscopic abrasives in the paste will embed themselves into the leather and are virtually impossible to remove.
Pull the strop out with one hand while pressing the blade flat against the strop. Maintain even pressure across the face of the blade while drawing the blade away from the edge. Begin your stroke with the edge facing you on the close end of the strop and draw the blade away from you. When you reach the end of the strop flip the blade over so that the edge is facing away from you and draw it back down the strop towards you. Continue alternating sides in this fashion until the blade is finely polished. For blades that are longer than the strop is wide, position the blade at an angle so that the entire length of the edge is on the strop.
To strop blades that do not have flat grinds you can use a strop that has been glued to a board. Establish the bevel angle and draw the blade away from the edge. Switch sides after each stroke.
If the strop is not polishing the blade well, make sure that there is enough polishing compound on the strop. The strop will periodically need to be cleaned and treated to remove excess paste, metal particles, and other gunk that accumulates on the strop. Cleaning and conditioning also keeps the strop supple and flexible.
Not all blades need to be polished on a strop or felt wheel. Most actually perform better without a polish. Polishing a blade removes the micro serrations left by the grit of final grind on a stone. This makes the knife easier to push through a medium, but reduces its ability to bite into the surface when being drawn. Regardless, all blades should be honed to a nice finish, and honing is the best way to maintain a blade for a long life.