I generally have 2 tests at the end. I cut a tomato to make sure the edge is where it should be. If I have done any thinning I also cut a large root vegetable to make sure I did not screw up the geometry. In between stones I cut into felt, and can tell its progression by how deep the cut goes.
I test only after heavy geometry change, or an unknown knife. My first edge after geometry change is often weak. With blades I'm familiar with, I'm quite confident. Perhaps very fine cigarette paper, for fun, or a three finger test before applying a single microbevel à la Jon Broida. My best test is Cr2O3 acrylic paint leather to be sure about burr debris.
There are a lot of parameters, but essentially you know long before you've reached your finest stone whether it will work or not - afterwards.
Thumbnail and three finger tests, those two will tell me what I need to know.
I like the Kramer test on enameled magazine stock - the slick stuff. Bend a page the try to cut the round part at a steep angle - now that's sharp. It's different for different tasks - a boning or slicing knife want a different finish. For boning not so highly polished - it's going to do some tough work and will get a touch up with the steel during the process especially if you are breaking down primals. For a general knife 6k followed by cardboard and newspaper strop works for me. For boning I go 1k. Deba or fillet knife maybe 3k they are doing tough work - and I still strop after the stone.
I go fight bears. Preferably grizzly bears. You will make sure your work is done properly when your life depends on the edge of the knife.
Unfortunately I have been officially banned from any and all federal parks, state parks, zoos, national wildlife preserves, carnivals....
I use the finger test and then try to slice through some thin paper
Hehe, I've been slicing an orange or grapefruit (I wanted to make some marmalade recently). If I can slice a less than 0.5mm thick slice off the orange through the central pith without crushing any of the juice cells, I call my knife sharp enough to use.
Paper is abrasive, I have no desire to waste the very shapest edge by cutting paper before I use the knife to cook with.
I just started the 3 finger thing a couple weeks ago and it's now a std for me. So -
1 - check for burrs runing my finger along the side of the edge and also to the edge. (direction is spine to edge) feeleing for any difference between the 2 sides and front to back. Same finger or thumb if possible.
2 - then the three fingers. that tells me no only how sharp the edge is but also how toothy or grabby it is. I never realized there was that much difference!
3 - slice a floppy paper towel to see how much pressure and clean the cut is.
4- then give it to my wife to shave a little skin off a grapefruit. A really really good edge doesn't cause the edges of the cut to "bleed" or weep. Then I start over until I get it right.
Peter - have you notices any dulling of some blades when slicing the peelings from grapefruit? My soft blades with way to thin bevels seem to actually lose the edge.
Originally Posted by psfred
when i sharpen kitchen knife I usually cut food with it and when its a chisel Im sharpening its usually wood.