Tool Talk: Knives, part 3 (sharpening)

You’ve got knives, so you need to take care of them. (If you don't have knives, go back to part 1 or part 2.)

Three big issues:

1. Daily maintenance
2. Maintenance sharpening
3. Heavy sharpening

Daily Maintenance
If you’re using stainless steel, ideally rinse and/or wipe your knife every time you switch ingredients, but certainly any time you stop cutting and go to something else (sauteeing, etc.) or switch from vegetables to meat to fish to vegetables and so on. Soap isn’t necessary except for hygiene: wash thoroughly after cutting chicken, for example. At the end of the day, wash very well with soap in tepid water, dry thoroughly, and put away.

If using carbon steel, do the same, but instead of rinsing and/or wiping, wipe with a very, very slightly damp towel every time you switch ingredients. When you finish cutting for the day (which is not the same as the end of the day: do this before serving dinner!), rinse very well in tepid water and then scour the blade: use a very stiff nylon sponge and plain liquid dish soap. Place the knife so that the blade is flat on a countertop or nylon cutting board, and scrub crosswise to the blade, from the spine to the edge, all the way along. Do this on both sides. Scour the handle quickly. Rinse very well in cool-tepid water until no trace of soap remains. Dry thoroughly with a clean dishtowel. Put the knife to "rest" somewhere dry and safe (out of reach of children!) for about half an hour, then put away; this resting period allows all trace moisture to evaporate rather than being trapped in a block or sheath. The scouring process takes less than 1 minute once you’ve done it two or three times.

If using a double-edged chef’s knife or cleaver, run it on a sharpening steel before use. To do this, hold the steel in your off hand, pointed away from you. Put the heel of the knife, edge turned either away from you or toward you, on the bottom end of the steel, nearest your hand, and angle the blade spine up from the steel about 15 degrees. Now slide the knife out and away from you, pressing down firmly. The object is to have the tip of the knife slip off just before it gets to the tip of the steel. Do this three or four times, then reverse the blade and do it again. Then two times on the first side, and two times on the second. The whole operation should take maybe 30 seconds. This does not sharpen a blade: every blade has thousands of tiny teeth, and as you bang on them they get out of line. A steel puts them back into line. But as you keep using the blade, those teeth get worn out, and then no amount of work with a steel will put an edge on.

Maintenance Sharpening
Every 2 weeks with carbon steel, and every month with stainless steel, you should get the edge back in shape. You can get away with half as often, but more rarely than that and you’re going to have to use coarser stones and really work at it.

I much prefer water stones, in the Japanese style, to oilstones. Oil is messy. Water leaves a small puddle, which is no problem. Japanese water stones are also very consistent in quality: a given grit weight is consistent across many stones, so you know what you’re getting. Regardless of the system you choose (and the grit ratings are different from system to system), get a medium-coarse stone, a medium-fine stone, and a fine finishing stone. Wash and store them according to package directions, or follow the instructions of the knife-store you bought them from if the salespeople seem very knowledgeable.

To prepare a water stone, start by dropping the stone in a big bowl of room-temperature water for half an hour. This impregnates the stone with water, which is necessary. When you're ready to sharpen, pull the stone out of the water and gently shake (don't wipe) off the water on the surface. To prepare an oilstone, you normally just put a small slick of mineral oil on the surface.

Your stone needs to be pretty firm on the work-surface. Water stones generally do this themselves, because the water plus the roughness of the stone fixes them solidly. Oilstones tend to slip quite a bit, but there are various systems for anchoring them, including special bracket things that clamp the stone and elevate it up off the surface, giving you a better working height and less mess.

Sharpening Method
After all that, the sharpening itself isn’t very difficult. There is some disagreement among professionals about the best ways, but here is what Aritsugu suggests.

Terms:
    Knife angle refers to the angle between the line of the stone (which normally passes through about your belly-button) and that of the knife. If you hold a knife straight out in front of you, the angle is 0 degrees, parallel to the stone; if you hold the knife parallel to the edge of the counter (assuming your stone is perpendicular to your counter), the knife angle is 90 degrees.
    Blade angle or edge angle refers to the angle of the plane of the blade with respect to the plane of the stone. If you put the knife flat on the stone, the angle is 0. If you put the knife on the stone as though trying to cut straight down through it, the blade angle is 90.
    The front of the blade is the one toward the outside of your body if you are holding the knife in your strong hand. If you’re a righty, and you hold the knife in your right hand, pointed straight ahead of you with the edge down and the spine up, the right flat of the blade is the front. The back of the blade is the other flat side.

Ready?

Hold the knife in your strong hand in a comfortable, normal manner. Place the front of the blade flat on the stone, and turn it so that the knife angle is about 20-30 degrees, so it’s pointed mostly away from you but the edge is toward you. Tilt the knife so that the blade angle is about 15 degrees from the stone.

Take a minute to look and feel. Get a sense for this blade angle, because you want to use it every single time you sharpen a double-edged blade under remotely normal circumstances (French, santoku, or Chinese-style knives for example). If you’re doing something weird, this blade angle will be a sort of reference point. So memorize it. Okay?

Put the three middle fingertips of the other hand on the back of the knife, close to but not at the edge, spreading them about as wide as the stone or a little less (not more). Take another second to memorize this position.

Now the job of those three fingertips is only to press the knife firmly but not as hard as possible down into the stone. The job of the strong hand holding the handle is to only move the knife up and down the stone.

Maintaining this position, slide the knife straight back on the stone until the far part of the edge is almost off the corner. In the same position, slide the knife straight toward you until the nearest part of the edge is again almost off the corner. Speed is not important. You do not want your strokes to be stuttering or shaky, but rather smooth and steady. Now do it again, until you have done 10 full passes, forward and back.

Lift the knife and with your off-hand thumb, gingerly feel the blade. To do this, place the broad ball of the thumb on the back of the blade, the flat and not the edge. Gently but firmly slide the thumb along that flat and off the edge, not over it.

You’re looking for a very slight roll-up or burr of metal. So what does that mean?

Think about what you’re doing here. You’re grinding the metal on one side, and you’re also pushing it at the same time. As you grind the down-side (the front), you’re simultaneously causing the up-side (the back) to bend up and away from the stone. This is what you’re feeling for: the roll-up of metal on the back. If you feel it, you’re done with this side. If you don’t, do another 10 strokes and test again. Don’t stop doing the front of the blade until you feel that roll-up. (If the ball of your thumb is very coarse or something, try the other thumb, or another finger, or whatever, but be careful.) It won’t be much, but you should notice it. If you do 30 passes and get no roll-up, try (a) a coarser stone, and (b) pressing down harder with your fingertips.

Now flip the knife over so that the edge is away from you, i.e. so that the back of the blade is down on the stone. This time you want the knife angle to be about 70 degrees or so, i.e. about as close to perpendicular to the stone as the other side was close to parallel to it. The blade angle should be the same, about 15 degrees. The three fingers will do the same work, pushing down, but obviously will feel a bit different on the other side here. Stop and memorize what this feels like, as before.

Now do 10 strokes, straight forward and back as before. Test: the roll-up on the back should be gone, and there should be a tiny amount — likely not much, but you never know — on the front. Keep going until you get this result. It will probably take the same number of strokes as it took on the front side.

If you have a long knife and a regular short block, you have thus far only been able to do a section, perhaps less than half, of the blade. Now that you have finished the first section, repeat everything in the next section of the blade, and continue until you have done everything evenly and equally. Err on the side of overlapping the sections rather than spacing them: you want to sharpen the whole blade.

If you have done this with a pretty sharp knife, using a fine or finishing stone, you’re done. If you need a super-sharp edge, repeat the process, first adding an extra slick of oil or a puddle of water to the stone (depending on which kind). Wash the blade as you normally would and store it as usual.

All of this elaborate description is of a process that takes about 20 minutes to do, and considerably less if you’ve got some practice with your equipment. Every month or so, if you find yourself wondering what to do this evening, just run through your main two or three knives this way, and bask in the feeling that you’re being virtuous.

If by some chance you are using a single-edged knife, Japanese-style, you have to make some adjustments. Fortunately, they will make your life easier. On the front of the blade, the side with the bevel, put the bevel flat down to the block and grind that way. On the back of the blade, put it again flat on the block. If you are passably assiduous about using a fine finishing stone, your knife surfaces will take on a mirror-like shine, for which reason these stones are sometimes called polishing stones.

The nice thing about this system, of course, is that you don’t have to worry about your edge angle at all: it’s built into the knife, and if you got it from a serious knifemaker it’s the right angle. The only problem, really, is that these blades can be very thin and flexible, and the fact that you’re sharpening flat can make you push down on the handle, bending the blade up in the middle just a hair and, more importantly, bending it down along the edge of the stone. Try, try, try not to do this. The other problem is that because you are grinding so much metal at once, relatively speaking, you will quickly start taking the surface off your waterstone, which is likely to stop being quite flat. That means you have to resurface your stone, which is a whole technique unto itself. Unless you have a lot of knives like this and sharpen them constantly (as you are in fact supposed to do, actually), I don’t think you really need to worry about resurfacing so long as you start with a new (and thus flat) stone.

If you are using both stainless and carbon knives, I’m betting you’re going to notice something rather quickly: the carbon knives are much easier to sharpen. The stainless, you have to work like a dog, but the carbon ones just seem to sharpen up lickety-split. Now do you see why a lot of professionals still swear by carbon steel?

Heavy Sharpening
Finally we come to the end. Whew!

Fortunately, this is easy to explain (and a good deal of hard work to do). About once a year, you sort of start over with your knives. You grind them coarse, medium, fine, and finish, all the way through. That takes off all the old metal surface and puts on a totally new edge, like a new knife. How?

You know your regular routine we just discussed? Do it on a medium-coarse stone. When you’re done, do it again smoother: add a slick of water to the surface of a water stone, or add a fair blob of oil to an oilstone. Then sharpen again on that.

Now move up to the medium-fine stone and do it over again. Add the slick and do it again.

Move to the fine or finishing stone and repeat, including the bit with the slick.

Now that’s an edge! You have spent probably an hour per knife, and have completely retooled the whole edge carefully and precisely. You have refined it to the best edge you probably have ever had, and you are ready to roll for another year.

But... what if you seriously screw up?

Okay, if you’re sharpening by hand, chances are you’re not ever going to do anything that could really seriously screw up a blade. The first time out, it’s probably best to start with a mediocre knife you don’t care about much, just until you get the feel of the thing, but after that it’s really not a difficult technique.

But what if you actually chip a knife in use, or drop it and chip it that way, or whatever?

A: If it’s a decent knife, and the chip isn’t hugely deep, take it to a hardware store and have them re-grind it on power equipment. The result will not be great, but it will be a blade. Now go and resharpen it, starting with the medium-fine stone, and work all the way up.

B: If it’s a mediocre piece of junk, resharpen it yourself, starting with a very coarse stone. You will not end up with a wonderful knife, but you will learn a great deal in the process. If you screw up or just can’t hack it, throw it away and get a new one.

C: If it’s a single-edged Japanese knife, you must (a) mail it to the knifemaker in Japan to fix, (b) take it to a specialist shop that knows about these knives and is into them, or (c) regrind it entirely yourself, being very slow and careful. Do not take it to a hardware store: they will not know how a blade like this works or is shaped, and will reshape it incorrectly, screwing it up royally and quite possibly permanently. I advise you never to be in this position: be careful with these things, okay?

D: If it’s very hard stainless, or ceramic, throw it away. Nobody can sharpen this: that’s why they say “never-dull”: it means “never sharpen, so don’t even try.”

Conclusions
So now you’re set. You’ve got the right knives for you, and you know how to take care of them. If you’ve bought high-quality stainless, the care is minimal. The only danger is that you will not sharpen them because those knives will let you get lazy; resist this, and sharpen every month.

Once you get used to a very sharp blade, you will know very quickly when your blades get dull. You will also wonder how you got along with mediocre, dull knives: a sharp knife does everything faster and better, with less work.

Love your knives, and keep them sharp.

Sayonara!