Monday, September 8, 2014

How a Serrated Blade Works

Serrated blades work on a couple of different principles. In general, you have a continuously variable cutting angle as you draw the knife in the cutting stroke.

(image courtesy of Sypderco via Amazon)

Other serration patterns exist too of course. I own a Victorinox 10" Bread Knife and New West Knifeworks Super Bread Knife. The Victorinox has had a best buy rating from Cook's Illustrated as it's a good performer for a very reasonable price. The thin blade is a little flexy for certain uses though. The Super Bread Knife is a very good knife for quite a bit of money and uses a less common gentle wave serration. I also like how the tip is un-serrated on the Super Bread Knife for a clean finish to the cut.

The Victorinox uses  a fairly common pointed scallop.

And both are chisel ground, meaning they're flat on the one side. Serrations are ground in with shaped wheels. As each wheel will wear somewhat differently, it's difficult to match up the pattern on both sides of the blade. A chisel grind is a reasonable solution.

For a given length of blade, a serrated blade has more total edge length than for a plain edge knife of the same length. There's more distance to a curvy route than a straight one. So for the same cutting stroke, a serrated blade can apply more cutting surface.

Serration patterns with points gain some sawing effects making serrations more efficient on fibrous materials. Further, those fine points concentrate the pressure on a small area increasing the apparent cutting power, but also increasing wear on the points.  The points tend to round over with time and use. 

Serrated blades seem to hold an edge longer. This is both true and false. The points of the serration are what contact the cutting board. The points take the abuse and are structurally more prone to wear and dulling.  Dave_Martell at Knifeforums has a very good photo of this as shown below.

However, the points are the least amount of edge on the blade and protect the curves from the more dulling aspects of cutting thereby preserving the overall apparent sharpness of the blade.

Performance differences 

Comparing my two serrated blades, they're fairly similar for cutting bread overall. The serration patterns behave a little differently. The pointy serrations start the cut in crusty bread faster. However, once into the bread, the super bread knife is a bit faster and creates less crumb on the board.

They were indistinguishable in cutting tomato. 

When making a long deep cut, as in cutting a cake horizontally for filling, the thinner more flexible blade of the Victorinox can wander towards the tip making for an uneven cut. Converserly, in a denser material, like squash, the thicker blade of the Super Bread Knife has more wander. 

There are some simple brackets to help you make the cake cut evenly though. 

Sharpening a serrated blade

The primary trick to sharpening a serrated blade is to find a sharpener with a radius equal to or less than that of the serration. Dave_Martell in the knifeforums link above demonstrates using Edge Pro sharpening films around dowels to do so. Spyderco's Sharpmaker has finely rounded corners on the triangle stones purposely for sharpening serrations, though it tends to round over the points a bit. Sharp round tips, but not as pointy anymore.  DMT makes some tapering diamond files for this purpose as well. Generally speaking, serrations are ground at 30 degrees on one side only. 

It is this fitment issue that precludes some serrations from being resharpened fairly simply and usually requires factory equipment to do so. This is the issue with Cutco style serrations for example. 

As the serrations get finer and finer, they become harder and harder to sharpen. Inexpensive knife sets often take this path to offer an initial sharpness and then just become food saws in cheap steel.

The wavy scallops on the Super Bread knife are easier to sharpen than the pointed scallops, at least on the Sharpmaker. It's not a big difference though.

Drawbacks to the serrated blade

  • Exaggerated glide to finish the cut. When the edge contacts the cutting board with just the points, the cut is incomplete. You have to move the points through the the rest of the cut to finish cutting. 
  • Most of the edge does not contact the cutting board
  • Requires special tools and techniques to sharpen
  • Marks the food when. cut Consider those steak knives that tear the steak more than cut it. Serrations are reasonable for a steak knife where they're used on hard ceramic plate that would dull a plain edge. But I don't like what they do to steak. You'll see the marks in other foods as well, even from a sharp blade. Waviness left behind and such. 
  • Wanders in the cut
  • Junk masked by serrations. Many inexpensive knives are serrated on poor steel because they'll still saw through pretty much anything
  • Impossible to sharpen some serration patterns without factory equipment. 

Thursday, August 28, 2014

Knife Skills: When to Guillotine and NOT Glide

So after the Craftsy knife skills class it may seem there is never a time to cut straight down through something. I suppose one could construct such an argument, most likely based around the exceptions having specialty dedicated cutting gear.

But most of us don't have or want a lot of rarely used specialized cutting equipment.

Most of the foods in this category have a weak but clingy structure such that the gliding action of a cut causes the product to break apart as it clings to the knife in its stroke. Cheese, various pates and terrines and so on. Cheese is probably the one most frequently encountered.

For my eating preferences, cheese is something I often want cut in thin slabs for making a sandwich or similar things. Just about every guide to cutting cheese has you breaking it down into wedges for serving and eating it plain or as part of a cheese course.

And that's useful to know too. So here are a few visual guides to cutting cheese from various shapes.

Cheese Guide from Australia
Huffington Post article on softer cheeses
Wikihow, but notice that this is a thick slab and not good for sandwiches

Prepping the Knife

Dedicated cheese knives often have holes or kullens (often called dimples, but more correctly kullenschliff) to break the clinging action of the cheese. Others use ridges to break up the sticking. On your chef's knife, you experience a similar thing with many vegetables clinging after a cut. Just as the holes or kullens work to break the sticktion, you can create a surface on your chef's knife that has the same behavior.

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Using a green Scotch Brite pad or equivalent when you clean your knife blade will scratch the surface up over time. On a Chef's knife, this is somewhat desirable in that it allows air in behind what you're cutting to minimize the sticking. It's not as effective as the holes, dimples or ridges, but you're making your one tool more versatile.

I like a tall knife for cutting cheese rather than a small knife like a paring knife. The tall blade rests against the cheese block during the cut and helps keep the slice an even thickness through out the cut.

I prefer a stainless knife to a carbon knife for cutting cheese. Growing up I had too many occasions where our carbon blade left a black smear of metallic tasting yuck on the cheese. Yes, the knife was not properly cared for as one in proper shape shouldn't do that. . Still, the experience soured me on carbon blades and cheese.

Keeping it Clean

Be prepared to clean your blade after every cut or every few cuts. As residue builds on the blade, this often aggravates the issue of the cheese sticking and deforming. You'll know when it's time to wipe the blade clean. On a similar note, you'll see people say to cut with wet blade or an oiled blade. This can help make a clean cut, but the oil or water residue is often just as undesirable on the cut cheese. No harm in trying it of course and seeing how you like the results.


Use the pinch grip. The pinch grip helps you keep the blade vertical. It WILL try to tip if it's dull or your pressure is not straight down. Using your off hand for additional pressure only compounds this effect, though I do use my off hand in this way. As with all knife skills, it takes some practice. There will be times the knife breaks free of the cut and plunges to the board with some force. This is not safe, nor good for the knife. It will happen as you learn. You must keep your fingers totally away from the edge, particularly with your off hand. No curling the fingers under. Do this at your own risk, and this is why dedicated tools exist for this task.

Ideally, your knife is long enough and the cheese block low enough that you can keep the knife tip on the board. This gives you more control and accuracy. But that won't happen every time.

This is not a quick drop as a guillotine, but a continuous even pressure. Avoid teeter-tottering the blade as that will lead to an uneven or failed cut.

In Use

Each knife will have a different minimal thickness it can cut evenly. This is related to the thickness of the knife itself. Here's my 10" Henkels with a broken cut and a plunge to the board in a brick of Tillamook sharp cheddar. I'm cutting too far forward for optimal pressure as well but some of that was from the jump.

Ok, my Henkel's isn't my sharpest knife and it's also on the thick side.  As you can see from where it snapped, I'm cutting very thinly. Too thin for this blade.

Again with the Henkels, this time it didn't break off mid cut. This slice is a little thicker than the previous one. But it cut thinly at the end as the thickness of the blade wedged it out of line of the cut. This is a serviceable slice for a sandwich but not ideal. Cutting the cheese even a little thicker would have solved this problem.

Here's a good cut with an 8" Ikea Slitbar in VG10. Very sharp, thinner blade stock. Even thickness for the whole cut. Notice its thinner than the last cut with the Henkels and even for the whole slice. Each knife has a minimum thinness it can cut. It will also vary from cheese to cheese by type and even within type as some bricks of the this cheese are moister and cling more. Occasionally you'll get a cheese that just refuses to cut well.

Here's an oblique shot to illustrate residue build up. The thicker Henkels builds more residue for more resistance and trouble in the cut. The Ikea being thinner has less residue. Still, towards the thicker end of the knife at the handle, you can see increased smearing and residue. You can see from the smears that I'm cutting straight through, no gliding forward or sawing which breaks the cheese apart. 

And an attempt to show blade thickness differences, Ikea in the foreground and Henkels in the midground. Even with the foreshortening distortion from perspective, the Ikea is still thinner.

Friday, August 22, 2014

Craftsy Knife Class Lesson 5

Lesson 5, Honing and Sharpening

As Brendan points out in the beginning of this lesson, this topic is deep enough for a whole series itself. What he demonstrates is simple, and uses commonly available equipment.

Within those limitations and to an audience who is not focused on high end knife performance, this is perfectly reasonable and complete enough for most home cooks.

I liked his grip trick for getting close to the edge angles for both "steeling" and the stone work.

Notice that his sharpening stone is pretty long. For sharpening kitchen blades, its best to use  a stone that is at least as long as the knife blade. Because you will make strokes the whole length of the knife, you need that long stone to have that much space. You can kind of fudge it on a slightly smaller stone or work in sections on too small of stones. But you're just adding to the work and aggravation to do that.

It's useful to have a few tricks to test sharpness. He cheated on the tomato test. To demonstrate the dull knife, he did  a pure push cut on an intact tomato. That's a really hard thing to do even with a scary sharp blade. There's a sort of holy grail test of knife sharpness that you can sharpen a blade to where it will push cut a tomato. Without a little sliding action to initiate the cut, tomato skin can resist a blade quite well. When he demonstrates his sharp blade, he slides it and it cuts easily.

The paper test is a pretty good one and he notes the simple things to look for. I usually use a piece of paper from the junk mail in my recycle bin. Newsprint is even better as it's flimsier and more revealing of edge flaws.

Any way, here's some paper cutting tests I did in 2012 for a particular line of small knives. Click to see larger versions and look at the edges of the paper. They vary in smoothness, feathering, folding and such.

Another hand test is as you're cutting potatoes. The cut surface of a potato should feel smooth and slippery. If it feels pebbley at all, it was cut with a dull blade. 

There is a set of downloadable pdf materials to complete the class. It includes a conversion chart for Metric to US and vice versa, pictures of the 4 knife types and some recipes as mentioned in the classes.

Thursday, August 21, 2014

Craftsy Knife Class Lesson 4

Shortcuts for Fruits, Vegetables and Herbs is the title of this lesson.

Paring Knife Use

Jalapeno with the spine of a paring knife, switch to a serrated blade. Notice how much rib and seeds were left behind with his choice of technique. It's a fine technique if you want a half of a pepper for filling or such.  And he's right, the skin on any pepper will quickly demonstrate if your knife is dull and you're doing a chop motion instead of a forward glide to finish your cutting stroke. I do prefer to have  the skin side up for cuttings same as Brendan does.

My preferred technique, yes even for small peppers like a jalapeno, uses the large chef's knife:

And he does this as well for bell peppers so I don't know why he didn't for the jalapeno. Perhaps just to demonstrate some options and let people use what they like best. 

Cauliflower, good technique, and better than I've done it before. I learned something new.

Citrus, good technique again, but the knife has to be sharper than most home cook's paring knife is likely to be. Even his microplane demonstration shows that they dull and become less effective over time. His was dull. A sharp microplane makes a fabulous fine zest without ripping or tearing. A vegetable peeler is likely to be a better tool for most home cooks to pare/peel the zest away. Then clean up the pith as as necessary. Or dedicated zester tools, though I've not yet found one that worked as well as I would like. If you need fine strips, a vegetable peeler and some knife work is my preferred method. Brendan flips the zest skin side up for the cutting for all the same reasons as the pepper.

Citrus supremes, he'd doing it right. The flat top and bottom cuts are important to this technique. One note about supremes. They're great presentation and flavor, but you lose fiber. Our diets are usually too low in fiber and an orange is often one of the higher fiber sources commonly available. This is one of the concerns about drinking fruit juice. It's so high sugar that without the fiber it's little better than soda at that point. Further, fiber slows and even blocks some sugar absorption in our gut. I suggest you save supremes for special occasions and eat smarter and healthier.

Serrated Blade Use

Tomato with the serrated knife. Notice that his circular cutting motions are now much longer on the glide part of the stroke. The edge of a serrated knife only makes contact with the board at the points. So you have to do a longer stroke to cut through the last part of the tomato. This is one of my peeves with a serrated knife is it's less efficient at finishing the cut.  A sharp Chefs is just as good if not better at this in my opinion. But that caveat of sharpness is important. For many home cooks, the serrated blade is their reliably sharpest blade. And if that's your situation,  using the serrated blade makes sense.

The grape/cherry tomato demonstration is a piece of genius.

Skipping over the peppers, because we discussed them above, Brendan demonstrates preparing a pineapple. He gives a little steering discussion for lefties as they'll have some struggles using the commonly available serrated blades more than the right handed users simply because of how chisel grinds are commonly done.  Notice that he keeps cutting on the right side of the pineapple from his perspective. If he tries to cut the side closest to him, he'll run into that steering problem because he's now cutting on the other side of the blade.

Butternut squash, technique is good of course. He clearly knows what he's doing.

Chef Knife Use

Avacado, it was good to see him demonstrate choking up on the blade. That's not something demonstrated very often.

Herbs, he's definitely not a fan of rock chopping and with reason. It's not as even or controlled mostly but less safe as well and damaging to the board and blade. I'm not going to tell you not to if you prefer it. I don't think this is an issue of significant merit in this case.  As to floating herbs, spinach, and such for cleaning, that's a good technique to have in your arsenal. Leeks, I can see the appeal, but there's enough grit in cutting the leeks up to that point you could be messing up your blade more than the somewhat simplified cleaning merits.

In summary, there's plenty of good ideas here. Brendan is a good presenter and keeps the lesson moving.  It's not especially insightful if you've been cooking a while as you've probably run across them. While he pointed out control and safety issues a number of times, I think he could have explained it more concretely and tied it back to the universal principles he laid out in Lesson 3. Breaking the squash down is not just about creating reasonable shapes. As with the onion, the breaking down cuts create flat stable surfaces for later safe cuts. That philosophy of cutting things will help you as deal with watermelon, cantaloupe, and other large food items.

Monday, August 18, 2014

Craftsy Knife Class Lesson 3

Lesson 3: The Board and Basic cuts

This was a good video, and I learned and refreshed some finer points of knife skills. I'm enjoying this class.

Cutting Board

Interesting he's using an edge/side grain board, not an end grain. End grain is usually what is espoused by wood aficionados. End grain self heals better but costs more. Edge grain can be prettier to my taste anyway. Also, I dispute his claim that pros prefer wood. Very few Health Departments allow wood cutting boards for professional food prep in contravention of his claims of harboring bacteria. Why? Because you can sterilize a plastic board, but not the wood ones. Sure there's the widely disseminated studies that show wood kills off bacteria on the cutting board. And while that's true to a certain extent compared to plastic, it doesn't kill ENOUGH bacteria to be safe. You have to wash your boards either way.

Grip and board stance

This is a topic that gets very little discussion. He offers very good grip info, good approach to the board. I'd have liked to see some discussion about using the whole board. Because of the angles of the arms in how you use the board, you have dead space, particularly in the corners. You can use that to store cut items, scraps and such to be efficient in your meal prep.

Low Cut

Slicing action--think Guillotine and Glide. The knife comes down, then slides forward to finish.  it's more elliptical than circular I think. Listen to the sound of his cuts. There's more of a swishing rub than the whack of a chop. He's doing it right.

His point about really only using the back half of the knife is important. It is for this reason that you are more efficient with a larger knife. Also, with a larger knife, the angles you work through are smaller reducing motion and work.

Another note, because he's cutting for the camera,  he deviates from the 45 degree angle he taught. Don't be fooled by the necessities of the filming.  the 45 degree work on the board is important for comfort, speed and safety.

When he's demonstrating the claw grip of the guide hand, note how awkward it becomes to raise the knife higher than the knuckle. The pinch and claw, guillotine and glide techniques work to keep you safe and efficient.

When he gets to the low cut summary at just past 12 minutes, the first bullet point is to keep the knife in contact with the board. This maintains the pivot point for the elliptical motion of the cut and is why correct technique for the low cut is so quiet. The knife glides on the board rather than impacting the board.

High Cut

When he demonstrates the high cut, there will be more noise, but not as much as you might think. Noise is a side effect of excess energy and poor technique. Use it as feedback on your technique.

Horizontal cuts in the onion. Notice he uses multiple strokes to make this cut. It' simplest, safest and more accurate this way until you develop a high level of skill. I still use multiple strokes on this cut particularly to not cut all the way through the root.

Onion, vertical and horizontal cuts
When he starts to pull back the knife for the second horizontal stroke. Notice how his knife thins from the heel to the tip. This is the distal taper. It's why you can easily pull back on the blade after it starts to wedge and get stuck. There are many subtle and important features to a chef's knife.

You'll see different chefs do vertical cuts before the horizontal cuts. I don't know that it really makes a difference, but probably I've seen more make the vertical cuts first on TV. I however, make horizontal cuts first. I find it easier. Do what you find easier but do try both methods.

On the vertical cuts, again notice that when he demonstrates poor technique, it gets louder.

Garlic-- this is one reason I don't like wood boards. It's very hard to get onion and garlic flavors out of the wood. As to his peeling technique, I've used it. It bruises the garlic and is not good if you only need a few cloves. Bruised garlic in the fridge gets really pungent and strong. I do use this technique when I need to prepare a lot of garlic for something.

He uses classic French technique for mincing garlic. It works, it's mostly for high end cheffing in my  opinion where the chef demands it.  For a full mince/paste I prefer the crush with the flat of the blade technique. His crush demonstration was too weak. Hit it harder and slide the knife a bit so the garlic comes apart more completely. Then the following mince doesn't have those large pieces. Alternatively, a press or a salt mince is good too.

While he doesn't mention it, he demonstrates another aspect of good knife technique. His knife is SHARP. He never forces the knife. Most of the work is from the geometry of the blade,  the sharpness, it's own weight and some light added pressure. This is also related to his onion commentary on good technique reducing tearing. The sharp knife helps a lot with this as well.

Sunday, August 17, 2014

Craftsy Knife Class Lesson 2

Craftsy Knife Class  Lesson 2: Knife Types and which to choose

Perhaps simplistic if you have much kitchen experience. This is, however, a class to cover the basics.

I disagree with the instructor over the value/versatility of a serrated blade for fruit tomatoes and such. If you're keeping your chef's knife sharp, it will do the job easier and better than the serrated blade for most users. Certainly individual taste varies as shown by the instructors recommendation.

I agree with him on the basic 3 knives a cook needs: Chef's, Bread/Serrated Utility and a paring knife. I'd opt for a petty or utility blade before a boning knife personally. And your general home cook would probably get more mileage from a petty compared to a boning knife as well.

My beef with serrated blades is that they're chisel ground, meaning flat on one side and angled on the other to meet and form the edge. On a knife a chisel grind wanders or steers in the cut. The denser the material, the more pronounced the steering effect is. You can compensate for it with practice, but it's a hassle compared to a sharp chef's knife. On bread and cakes and such, it's not such a big deal as that material is fairly soft. Also serrated blades require somewhat specialized equipment to sharpen and some types can't be sharpened at all.

MAC makes a bread knife with a conventional V grind, but I've not used one to have an opinion of it.

At the end, he demonstrates a simple trick on a ceramic cup for touching up a blade if you lack equipment. He's not wrong, but I want to emphasize you find one with the finest smoothest texture or you'll probably do more harm than good.  Similarly, there's an interesting bit in Spyderco's Sharpmaker instruction video where Sal Glesser (owner of Spyderco) shows sharpening on a non-glazed large clay pot just to show what can be done.

At the 3:50 mark in this video, Mr. Glesser shows that technique.

I'd have liked some more discussion of profiles, steels, and such. So let me give you some links for some of these concepts. 

French vs German knife profiles. You're probably more exposed to the German profile than the French or the derived Japanese profile. 
Gyuto- the Japanese Chef's knife

The Kitchen Knife Forums sticky topics This is a set of information that may be deeper than you ever wanted to know, but offers a good jumping off point it you want that kind of information.  Steel, design, terminology, makers and more. 

On the other hand, it was refreshing that he skipped over forging vs stamping, bolsters, rivets, full tangs and such. Good knives can be made with or without those things. I do have a point i want to make however. Full height blade bolsters. I do not like these. This picture from my Henkels Chef knife should exhibit my issue.


Notice that where the edge meets the bolster that the edge has worn up the knife from sharpening. The bolster now drops lower than the edge. This means that my full edge does not make contact with the board so things don't get cut all the way through. Now, yes, I can grind that down or have it ground down. But I shouldn't have to. The design itself is poor. 

With that close up view, it seems that whole edge could use some work. It has been some time since I used or sharpened that blade.

And some links on the the disputable issues.

Forged vs. Stamped This page has some good photos of knives at different stages of forging and stamping. I link it for the discussion of method, not their conclusion. I disagree with the conclusion that stamping is automatically inferior. Many high grade particle metallurgy steels can be stamped or laser cut into great knives of equal or better quality than mass produced forged blades.

Full Tang vs. Stick Tang via the Kitchen Knife Forum discussion of the topic and a useful knife anatomy link showing some diagrams of the designs as well. The rivet issue is part of this discussion actually. My Henkel's chef knife does not have a visible tang or rivets but it's a decent knife. I'd choose a gyuto if I were to spend that much in todays market.

Bolsters or No Bolster Zknives discusses forged/stamped, but the last half discusses the bolster issue. Bolsters can be done to not interfere with the sharpening of  the blade. If you like them, great, if not, that's great too.

Friday, August 15, 2014

Craftsy Knife Class and Lesson 1

Craftsy is offering an on-line video course on knife skills. It requires an account (an email address and a password) to access. So free from monetary payment, but they'll likely market to you afterwards.

If you want to take this course, be sure to read their Terms of Use and their Privacy Policy to be sure it meets your expectations.  One of their terms of use is that they may withdraw an application at any time so this class may not always be available or free.

I'm always interested in learning new things and brushing up my skills, and the price was right so I signed up. I'll make a review post with my comments and related insight for each lesson. They'll make sense in the context of the lesson, but might be disjointed if you read them without also watching the lesson. Hopefully it will help you decide if you want to take the class or offer alternative perspectives if you do take the class.

The first lesson is a short introduction to the Craftsy classes. It's just under a minute and is mostly self promoting their site which is to be expected. So the rest of the posts will begin with lesson 2.

Lesson 1: How to use your free mini class
Lesson 2: Introduction, which knives you need
Lesson 3: How to make the basic cuts and demonstrations of those cuts
Lesson 4: Further demonstrations on specific fruits and vegetables to help ou be efficient at each task
Lesson 5: Sharpening and Maintenance

The lessons vary in time, from 8-43 minutes, but you can skip around in the video or return to it later as needed.

See you in class.