Ceramic Knives - Why We Don't Sell Them - Knivesandtools

Sharpness after use

After cutting, all the knives undergo the sharpness test again. In this test the ceramic knives perform considerably better than the steel knives. The test proves they do stay sharp for a longer amount of time. In using the knives we have not felt the difference in sharpness between ceramic and steel knives. This is because sharpness test only measures the sharpness of the blade itself. The geometry of a blade plays a big role in how the knife feels to the user. It is possible that a knife does not do extremely well in the sharpness test, but due to its geometry it can still cut really well. We also note that the ceramic knives are all thicker than the steel knives.

Sharpening ceramic knives

The next step is sharpening the blades. The steel knives we sharpen on Naniwa Chosera stones up to grit size 5000. For the ceramic knives we have used a battery charged diamond sharpener. Ceramic is such a hard material it can only be sharpened by diamond. It is difficult to get an even sharpening result with the diamond sharpener. The knives do get sharp but it takes quite some time and effort to get rid of the chipping on the blade. The machine also jams often, so we are not very positive about this means of sharpening.

The ceramic knives can be sent to the supplier to have a professional sharpen them. The box the knives are shipped in contains a voucher which can be exchanged for sharpening the knives. The problem remains you cannot use the knife for a certain amount of time and have to pay shipping costs. Just doing quick maintenance on your knife at home, with a sharpening rod or whetstone, is impossible. For steel kitchen knives there are many different possibilities to sharpen them at home or give them a quick touch-up.

The twisting test

On the packaging of the ceramic knives it says they are unsuitable to twist and flex with. However, it is impossible to prevent some sideways pressure on the blade at all times. The twisting test also says something about how it can withstand falling so we have tested al the knives on this.

In this test a U-shaped holder is placed over the blade. The holder is twisted and we measure how much force we have to apply before the blade breaks. The Kyocera of 18 cm’s did pretty well with 0,33Nm. Even better than the thinly sharpened carbon steel knife we have tested, which broke with 0,30Nm. The Kyocera 13 cm knife did not do so well and breaks with 0,08Nm. When we tested a thin VG-10 knife of a big Japanese brand we could apply 7,75 times more pressure compared to its ceramic counterpart with 0,65Nm. The Wüsthof Classic knife we tested wins the test easily with a 1,34Nm.

The cheap ceramic knives do not come close to the Kyocera knives. One knife even broke when we put the holder on the blade to start the test. The difference between the cheap ceramic knives and Kyocera is not just the price and sharpness, but also lies in the quality of the material.