When sharpening for a hair-popping experience, the keenness of the edge will reach a point when the thumbnail riding test (where you "leap" off the edge when the tip of your thumbnail, to see if it catches on the burr), and the light test (where you shine a bright light directly on the edge, to see if it's completely straight [i.e., no leaning burr]) will neither work. In that case, I've found the following is what I need to use:
Laying the blade on your arm, choose an angle. I typically use 30-40 degrees. Without any downward pressure, draw the blade along your skin. It should be shaving at this point, or even better, snagging the hairs lustily, and sending them flying.
The more acute the angle, the less well the blade will cut hairs. The more obtuse the angle (i.e., the blade is more perpendicular to your arm), the easier it will cut. This difference is the basis of the test.
Now, draw the blade on your arm, at 30 degrees. Note exactly how easily it cuts the hairs. Feel for the "grabbiness" of the edge. Now turn the blade over and repeat, using the same angle. If your edge is perfect, with no burr leaning either way (or a burr that is perfectly straight), your blade it will cut equally as well on both sides. This is REALLY rare, if you're not trying to achieve it.
How does one side cut better than the other? Well, the burr is nearly always bent to one side or the other (it was bent by your sharpening stone, on the last swipe, that's how fragile it is). Let's say you're holding the blade against your arm, and the hairs are just running away. If you're not done sharpening yet, this means that the burr is bent *toward* your arm, making a more obtuse angle, which cuts much better.
You flip the knife over, and its cutting ability degrades. This is because the burr is now bent away from your arm, making a more acute angle, which cuts less well.
The side that the burr is now pointing toward needs a single, very light stroke on your stone. Or, if you're done grinding and want to be rid of the burr, grind against the stones (*very* lightly) using a highly obtuse angle. Repeat this for both sides. Conduct the test again. Continue smoothing the edge, ever more gently, until the blade cuts equally well on both sides.
At this point, you should have an edge so keen that it's nearly a burr itself, but is aligned and centered so that it will push-cut nice and straight. Use a smooth butcher's steel to realign this super-fine edge regularly, since ordinary work will bent it really easily (unless you're using an extremely hard metal, say Rc 62 or higher).
This kind of edge works wonders in the kitchen, especially if you grind at fiften degrees a side. Watch out, you recalcitrant vegetables!
Laying the blade on your arm, choose an angle. I typically use 30-40 degrees. Without any downward pressure, draw the blade along your skin. It should be shaving at this point, or even better, snagging the hairs lustily, and sending them flying.
The more acute the angle, the less well the blade will cut hairs. The more obtuse the angle (i.e., the blade is more perpendicular to your arm), the easier it will cut. This difference is the basis of the test.
Now, draw the blade on your arm, at 30 degrees. Note exactly how easily it cuts the hairs. Feel for the "grabbiness" of the edge. Now turn the blade over and repeat, using the same angle. If your edge is perfect, with no burr leaning either way (or a burr that is perfectly straight), your blade it will cut equally as well on both sides. This is REALLY rare, if you're not trying to achieve it.
How does one side cut better than the other? Well, the burr is nearly always bent to one side or the other (it was bent by your sharpening stone, on the last swipe, that's how fragile it is). Let's say you're holding the blade against your arm, and the hairs are just running away. If you're not done sharpening yet, this means that the burr is bent *toward* your arm, making a more obtuse angle, which cuts much better.
You flip the knife over, and its cutting ability degrades. This is because the burr is now bent away from your arm, making a more acute angle, which cuts less well.
The side that the burr is now pointing toward needs a single, very light stroke on your stone. Or, if you're done grinding and want to be rid of the burr, grind against the stones (*very* lightly) using a highly obtuse angle. Repeat this for both sides. Conduct the test again. Continue smoothing the edge, ever more gently, until the blade cuts equally well on both sides.
At this point, you should have an edge so keen that it's nearly a burr itself, but is aligned and centered so that it will push-cut nice and straight. Use a smooth butcher's steel to realign this super-fine edge regularly, since ordinary work will bent it really easily (unless you're using an extremely hard metal, say Rc 62 or higher).
This kind of edge works wonders in the kitchen, especially if you grind at fiften degrees a side. Watch out, you recalcitrant vegetables!