Advanced Techniques — Convex Edges, Mirror Polishing, and the Hamaguri Edge

For those who want to go deeper, there are techniques that go beyond the basics and into the territory that separates good sharpening from exceptional sharpening.

Convex Edge Sharpening (The "Appleseed" Edge)

A convex bevel — where the bevel curves outward rather than being flat — can't be created on a flat stone alone. It requires stropping with progressively lower angles to "roll" the flat bevel into a gentle curve. The technique involves:

1. Start with a flat bevel established on the stone.
2. On the strop, reduce the angle by 2–3 degrees from your sharpening angle and make 10 strokes per side.
3. Reduce by another 2–3 degrees and make 5 strokes.
4. Then 3 strokes. Then 1 stroke. Each set of strokes at a lower angle gradually rounds the bevel into a convex curve.

The result is a stronger edge at the apex — more supporting metal — while maintaining sharpness. Recommended for hunting knives and outdoor knives that see rough use.

Mirror Polishing

A mirror-polished edge (where the bevel looks like a mirror) requires working through all grits up to 8000+, then stropping extensively on progressively finer compounds. The bevel surface reflects your face like a mirror when properly polished.

Mirror polishing is mostly aesthetic (it looks extraordinary) but does provide a functional benefit for certain applications: a mirror-polished edge on a straight razor or a Japanese pull-cut slices with less drag because the surface is so smooth it barely creates friction.

The Hamaguri Edge

The "hamaguri" (clamshell) edge is a Japanese term for a specific convex edge geometry where the bevel curves outward from the spine all the way to the apex, like the underside of a clamshell. It's the geometry produced by hand-sharpening without a guide on a slightly domed stone. The hamaguri edge is considered by many traditional Japanese craftspeople to be the ideal geometry for a kitchen knife — strong, sharp, and beautiful.

You achieve it through freehand sharpening with circular or figure-8 strokes that vary pressure along the bevel surface and gradually produce a subtle convex profile.

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