Where the Marker Disappears: Reading Your Angle

The problem with freehand sharpening

Yesterday we covered grits — 400 to 6000, stepping rather than skipping. Today the harder skill: holding an angle without a jig.

A jig clamps the blade and fixes the angle for you. Freehand, your wrist drifts. You start at 15 degrees, finish at 22, and the edge is round instead of sharp. The knife feels dull even though you spent twenty minutes on the stone.

You cannot feel 15 degrees. But you can see it.

The marker test

Color the bevel — the 刃先（はさき）edge area — with a black marker. One pass, full length on both sides.

Now take one or two light strokes on your 1000-grit stone at the angle you think is correct. Look at the bevel.

• Ink gone at the very edge (the 刃先, hasaki): your angle is too shallow. The stone is only touching the tip.
• Ink gone across the whole bevel: correct. The stone is matching the existing angle.
• Ink gone at the back of the bevel, near the 峰（みね）spine: your angle is too steep. You are grinding the shoulder, not the edge.

Wipe the marker off with a cloth and alcohol, or just sharpen through it. The ink disappears into the stone slurry.

The 15-degree block

Most 包丁（ほうちょう）kitchen knives — gyuto, santoku, petty — are ground at roughly 15 degrees per side. Some Western-style knives are 20. You do not need to guess.

Cut a small block of wood at 15 degrees. A 15-degree wedge is about 1 in 3.7 — so a block 37mm tall and 100mm long gives you the slope. Set the blade on the stone and slide the block under the spine until the angle matches. That is your reference. After a few sessions your wrist remembers it.

You can also buy a cheap angle guide. There is no shame in it. The point is to learn the angle, not to prove you can guess.

Why the angle matters more than the grit

A 1000-grit stone at the wrong angle leaves a worse edge than a 400-grit stone at the right one. The angle controls the 角度（かくど）geometry of the edge. Grit controls the scratch pattern.

If you are sharpening a 三徳（さんとく）in your city and it will not cut tomatoes, check the angle before you reach for a finer stone. The marker test takes thirty seconds. A wasted hour on the 6000 does not.

The bevel tells you what happened

After the marker pass, look at the bevel under a lamp. A clean, even strip of bare steel means you held the angle. A patchy, uneven strip means your wrist moved. That is information, not failure.

If you are sharpening a 出刃（でば）or a single-bevel knife, the rule is different: you sharpen the flat back and the beveled front, and the marker test still works, but only on the beveled side. Single-bevel knives are a separate lesson.

For now, the double-bevel 包丁（ほうちょう）is your practice ground. Use the marker. Use the block. Check the ink.

What to do when the ink is right

Once the marker disappears evenly across the bevel, you know your angle. Now sharpen normally. Check again every few minutes — your wrist will drift. Re-mark if you need to. Nobody sharpens a knife perfectly on the first try, and the marker does not judge you. It just tells you where the steel met the stone.

Tomorrow we raise a burr on both sides. That is the moment the edge actually forms — and you can feel it with a fingernail.