Can ceramic knives be sharpened?
I was just looking at an ad for Kyocera ceramic knives that look pretty nice. The ad stresses that they retain their sharpness for a "long time" and they are warranted for five years (? for retaining sharpness??). Does anyone have any experience with these knives? Can they be sharpened at home? by the factory? or, not at all?
The factory can do it. A very skilled sharpener with very fine diamonds can do it.
I think ceramic blades make sense for a limited number of purposes, and kitchen knives aren't among them.
I bought one (chef's knife shape for chopping) about 10 years ago. Loved it for certain things for about 2 years, then noticed it wasn't doing the job so well. Sent it to the factory for sharpening (it was an easy process) and it was good for another 6 months to a year. These are expensive knives. I wouldn't recommend that anyone buy one for general kitchen use. It was a joy when it was new, though.
More often than not, the factory will sharpen a ceramic knife for a fee. You can decide if the fee is worth it. Realistically, that's usually your best bet (that or buying a new one - prices have fallen).
The electric sharpener Caroline1 linked above might work. I dunno. It's not a well known product and I haven't seen any especially credible reviews of it.
I haven't tried to sharpen a ceramic knife, and truth is I probably wouldn't unless I had one sitting around that I didn't mind possibly making worse as well as some diamond stones.
From what I've read though, it is possible to do at home - with diamond stones. Possibly even with wet/dry sandpaper. There are several problems though - I've heard that a coarse DMT will usually take chips out of the edge, meaning you're limited to fine grit. You also should probably refrain from using much pressure for the same reason. This means it might take a long while. Also, you shouldn't expect a burr to form, which might be a problem if you (or whoever, since this is clearly addressed to people already familiar with hand-sharpening) rely on finding a burr to know when you've hit the edge.
Even then, I couldn't guarantee it would work. Dave from DR sharpening claims to have had success with hand sharpening ceramics like this though.
Thing is, if you're willing to hand sharpen in the first place, you may as well get yourself a nice traditional knife and just keep a fine edge on it.
I hand sharpen everything and have done so for years (an electric sharpener ruined the finish on a really nice SOG knife I had and I've been wary of them ever since.) There are basic problems with hand sharpening that a good ceramic addresses:
First is time. I hand sharpen semi weekly and use a basic steel daily to keep the edge on a steel knife. They'll cut tendon and butter equally but it takes time and attention to angles to maintain that.
Second is cleaning. Every time I sharpen a knife I have a stone to clean, oil to wipe up and a blade to clean. steel dust gets everywhere and the last place I want it is my food. i sharpen steel knives either weekly or every 2 weeks if I'm busy.
I sharpen my ceramic knives on a diamond stone bi-montly and they're just as sharp as the steel, if not sharper (on average)
I use a fine/medium diamond stone by RedHead that I picked up at Bass Pro and it's kept my ceramic knives in fine condition without chips
I sharpen with 4000it grit Shapton Glass waterstone every other week. It takes 45 seconds, and all I have to do is wipe up water and slurry afterwards--which takes 10 seconds. Every couple of months I'll break out a 1000 or 2000 Shapton Pro to thin behind the edge, but it doesn't take much more than 3-5 minutes per knife. If you have time to cook, you have plenty of time to sharpen. You can whittle hair with the edges I get off of the stones, and I haven't even stropped with compound.
I've only ever had issues with steel dust with diamond stones.