Posted on 10 Oct 2015 00:16
So, you've heard you can get a knife made out of the same type of stuff as the mug you use for your morning cup of joe? And these knives are mega-sharp. So, sharp they make those Ginsu knives from years back look like a rubber hose. But, it's ceramic. So, it is so very fragile, and for sure you can't cut through an aluminum can or a nail like with a Ginsu!
The leading maker of Japanese Ceramic knives, Kyocera, certainly makes a sharp knife. But, just how sharp is it? And if it is ceramic, is it really practical at all? Or will it just shatter unless you do anything but carefully slice tuna for sashimi, like a Japanese Sushi chef?
The Key to Sharpness is Hardness
Good questions! Let's start with how sharp a Kyocera or other ceramic knife might be. Well, the key to how sharp the material can be is its hardness. In terms of steel, you might hear knife makers telling you how hard their steel is, to make you want to buy their knives. The hardness of steel is described by the "Rockwell number." With kitchen knives, you're probably getting a Rockwell number of somewhere between 54 and 64. The higher the number the harder the steel, and so the more potential for sharpness.
Sharp Like a Surgeon's Scalpel
Ceramic knives are made of material that is twice as hard as the hardest steel. This probably doesn't mean that they can be sharpened to an edge that is twice as sharp, but, they are as sharp, if not sharper than any razor blade.
With a ceramic blade, you're basically getting a blade that compares with a surgeon's scalpel, and they will glide through a piece of tuna just like a scalpel glides through flesh, producing a clean cut.
It is probably not true to say that ceramic knives are sharper all steel knives, but they are sharper than any steel knife you are bound to own, or ever own.
A video demonstration is probably the best way to see the sharpness of a Kyocera ceramic knife. Yes, the knife looks like a toy to me, as well, but it is not something with which to play! Look how sharp this knife is:
Will Ceramic Knives Shatter Like Glass?
Now, back to the material. It's not the same type of "ceramic" as in your coffee cup. And, no, although you may have heard that these ceramic knives will "shatter like glass" if you drop them or knock them against something hard, that is not really true. The material is brittle, and you could chip a piece of the blade away, and that would not be good, but it's not like dropping your coffee cup. Heck, it's not even like dropping your iPhone.
How are Kyocera Ceramic Knives Made?
Kyocera, the first company to produce these ceramic blades, and the largest manufacturer today, makes its a material called zirconium dioxide. This may sound familiar. If you're thinking fake "cubic zirconia" diamonds, you've got it. Cubic zirconia is a crystallized version of zirconium dioxide. It is an extremely hard material and the blades are about 50 percent harder than steel.
The company makes the knives with zirconium dioxide,which is mined from Australia (go figure). They grind it into a powder. They then mix it with water and continue to crush it into a pasty sludge, which is then dried to leave behind an extremely fine powder. The powder is put into molds, and the molds are subjected to three hundred tons of pressure, which binds the powder into a solid knife shaped blank. The blanks are put into a very hot furnace and baked to harden them. After they are out of the oven, a handle is attached and the blades are ground, honed, polished, and buffed to a shiny white (or black) knife that resembles a plastic toy, but is anything but.
Light as a Feather (not really but super-light), and Super-Sharp
As you can see in the video, the ceramic knife is super-light. Compared to your heavy steel chef's knife, it will feel like a feather in your hand. The lightness of the knife should tell you something about its so-called potential to shatter. It is not as heavy as a glass or a ceramic cup. It is a fraction of the weight, and therefore the impact it makes when you drop it, impart less force, and therefore has less potential for damage in the first place, even if it were so fragile, which it is not.
In fact, some cooks may have a hard time adapting to this light-weight feel, and they may not even like it. However, in the demonstration, the knife glides through yellow bell peppers just by the slight weight of the knife alone.
It is sharp, sharp, SHARP!
What's more, it is smooth. Stuff doesn't stick to the sides of the blade like your average steel knife. In fact, this lack of friction is actually something that aids in slicing, and help to slice super-thin slices of soft meats, or tuna, of course.
Good for "Normal" Use, But What is Normal?
I've read that ceramic knives are good for "normal home use." Well, normal for me may not be normal for you. don't go thinking you can attack a watermelon with it. For everyday work, like chopping vegetables, fruits, and boneless meat, they are a whiz. But remember, they have virtually no flexibility, are hard and brittle. Knock a ceramic blade against a chicken bone and you'll probably end up with a chipped edge. Try to smash a clove of garlic…don't do that. I think you get the picture. I use my awesome steel chef's knife like a hammer (yeah, I know, I know). You have to be respectful of a ceramic knife: its awesome sharpness and its fragility.
Still, ceramic knives aren't so fragile they are impractical. They will keep their edge for years, if used with care. But, once it loses its edge, you can't just hone it with few swipes of the steel, or take it to your local knife sharpener. You have to send it back to the manufacturer, the only people with the ability to sharpen these things (so it is claimed).
Well, apparently this is not the case any longer. Kyocera now offers an electric ceramic knife sharpener. They will, of course, sharpen your Kyocera ceramic knife for you, and they do still offer a lifetime service, should you ever need it. I know what you're thinking: I have to ship my knife to Japan? No, Kyocera is a big company. They have facilities in the states.
The video below provides a demonstration of a Kyocera electric ceramic knife sharpener in use.
I also came across this video of how Kyocera sharpens their ceramic knives. Grinding wheels. There is nothing mystifying going on here. This is at their Orange Country, California facility. If you're like me, you're thinking, I thought these things were supposed to never need sharpening, you say? So, why all the talk about sharpening? Well, look at the stack of boxes in the video. They all have ceramic knives in them, shipped to Kyocera by customers. So…there. They will stay sharp for years, with careful use, but regardless, I don't think most knife companies provide life-time sharpening.
Given the juxtaposition of a professional carefully sharpening the blade of a ceramic knife in the second video, and the electric sharpener at use in the first, which looks much like any electric knife sharpener, except perhaps for the actual grinding wheels, I'm a bit skeptical. We know that electric knife sharpeners don't work. At least, I know they don't. I had one sitting around for years after I discovered that it did NOT properly sharpen my good knives. It was a door-stop, at best. However, I don't see why the company would produce a sharpener that did not work, or potentially damaged the knives, while still offering lifetime service or replacement.
Surely, Ceramic Knives Cost Hundreds of Dollars
Nope. If you like the idea of a razor sharp ceramic knife that you can cut your finger with but get no scar because the cut is CLEAN (just kidding), it is quite practical to own, even if it can't really be your only knife.
In fact, you can get a Kyocera 3-piece ceramic knife set for 80 bucks. It comes with a 6-inch Chef's knife, a 5-inch micro serrated knife which I would call a utility knife, and a 3-inch pairing knife. All for the price of a one high-quality steel chef's knife, but not even a top-shelf one.
A 6-inch chef's knife may be a little small for many cooks, even if you don't need the added weight of a large knife. They offer a 7-inch ceramic professional chef's knife, which comes in their special black series which is supposedly more durable. It goes for a bit over 45 bucks.
Also, if you know anything about Benriner Japanese mandoline slicers, you might be thinking, why don't they make a mandoline with a ceramic blade? Yep, Kyocera makes one of those.