This is the 4th 'can you sharpen on it' video and in this one I am attempting to sharpen a knife on a clay brick. After soaking in water I lapped the clay brick with another clay brick until the surface was flat. I also rounded the edges. It took 5-10 minutes to do this and you had to use plenty of water.
The sharpening took me about 10-15 minutes. As the sharpening went on I could feel the sand and little stone inclusions in the brick begin to stick up more and more as the clay was worn away. If you were to try this method of sharpening I would recommend lapping the brick again every 5 minutes or so of sharpening.
I was quite impressed with the result. It isn't a perfect edge by any means but it it more than sharp enough to get everyday tasks done.