Sharpening a black ceramic kitchen knife

Great post! Thanks for the detailed info. I have been telling people to toss them and get another if you must have ceramic.
 
pwet said:
hum nope, if the final angle at the very edge is steeper, it will be weaker. in fact that may sound counter intuitive but if you measure the apex angle of any convex and replicate a v edge with the same angle the convex edge will always have less material behind the edge.
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But there are no shoulders to get hung up on creating tangential stresses from the material you're cutting and lateral forces at the edge are directed through the arc. If you do a brass rod test on the two edge profiles using the same steel at the same rockwell, the edge deflection on the convex edge will be less for the same amount of force applied, because the stress is better distributed.
 
Slicing the same kind of tomato with an older white ceramic knife i sharpened for testing purposes in my own kitchen:

 
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IMO the magic word when it comes to reprofiling & sharpening ceramic blades is "dampening": you will need to find ways to soften the constant impacting of the sharpening grits (be it silicon carbide, cbn or diamond) on the ceramic material, or you will end up with a crumbling edge as the ceramic has such a low toughness.
This crumbling effect will also increase as the knife edge gets progressively thinner from grinding/sharpening.
That's why i use the black silicon stone on the Tormek for reprofiling (since it basically grinds under water), as well as various Paper Wheels for the necessary refinement, since these have just enough "give" in them to smoothly sharpen ceramics (when used with diamond compound)

I have no experience with using a DMT plate for sharpening ceramic knives, but when these were all i had i would probably take my finest DMT plate and try to sharpen the knife while holding both the plate and the knife under water, using indeed the edge trailing method with light pressure.
No guarantees, but i have a hunch it might work.
Remember that if it does the resulting edge will need refinement, as you don't want a toothy edge on a ceramic knife.
Fine wet & dry paper will work (be it slowly), but maybe you can even find some diamond paper.
 
I'd advise using a heavy lubricant like dish soap or oil and placing the dmt plate on a folded thick towel or foam pad.
 
Thanks for tips. Especially the 'dampening' aspect. I'll give them a try and update again.

PS: inspired by the slicing tomato video :)
 
Sorry to revive a dead thread, but I'm hoping Kwackster is willing to say exactly which products he uses for this purpose. Thanks
 
I already wrote down how i do things in this thread in post #20, but if you have more specific questions: fire away :-)
 
I have sharpened several ceramic knives using DMT plates with no attempt at cushioning, so if you're careful that isn't really necessary. Just be certain not to push very hard -light pressure is key. People always say to let the diamonds do the work when using diamond stones, and not to apply pressure, but in this case it's mandatory or you'll chip the edge immediately.
 
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