Diamond sharpening stones - poor product or my technique?

[Grunff]

I recently bought a set of diamond sharpening 'stones' to try them out:

I've used them a few times now, mainly to sharpen knives. The first couple of times they seemed to work pretty well, giving a nice edge quite quickly. But now it seems that much of the diamond has rubbed off the steel backing. They don't sharpen so well.

I've been using them dry, and in much the same way one would use a dry stone to sharpen a knife. Is it my fault, or do they wear down quickly? Experiences?

[Weatherlawyer]

They need a lot of water. Still, you will be able to replace it a lot easier these days. They used to cost a weeks wages. I believe they are now quite cheap.

I was amazed at how fine a polish the coarse side of mine puts on my blades. I can't seem to get the hang of finishing them on the fine side though.

But the edge it leaves on the coarse side is still pretty good.

[Andy Dingley]

There are two sorts - monocrystalline diamond and polycrystallines. Polycrystalline diamonds are soft (in bulk) and wear down in no time. If you buy a cheap diamond stone then it will wear out quickly. If you want it to last, get a DMT or Eze-Lap.

The plating is nickel plate over steel. Nickel is permeable, so always dry them off after use wet, or else you can rust them and get pinhole rust spots.