Under magnification, a used knife edge can show scratches running in several directions. In one illustrated sharpening sequence, those marks become more aligned as a rough stone reshapes the bevel, honing works toward the apex, and polishing smooths the edge. The images reveal changes to the surface—not a measured sharpness score or proof that the knife will cut better or stay sharp longer.
What the microscope shows during sharpening
Make: published Caleb Kraft’s illustrated demonstration on December 4, 2015. It follows one used knife through rough-stone shaping, honing, and polishing. The sequence is useful for seeing how the edge’s appearance changes, but it is not a controlled test: it reports no calibrated instrument readings, numerical sharpness result, or edge-retention measurement.
Before sharpening: mixed wear marks
The used edge shows scratches in multiple directions. Kraft also describes a nearly flat ridge that reflects light toward the microscope. That reflected line is a visible feature of the edge in this example, not a standardized measure of how dull the knife is.
Rough stone: shaping the bevel
The rough-stone stage works on the cutting area and establishes a more uniform angle in the illustrated sequence. The surface begins to show a more consistent scratch pattern. A sharpening stone or whetstone is used to remove metal and reshape an edge; the right angle and method depend on the knife, rather than on a universal setting.
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Honing: working toward the apex
As the bevel becomes smoother, the demonstration describes the thin edge as curling. This curled line is a burr: metal displaced along the apex as the two sides of the bevel are worked. A burr can be extremely small, and a view of only one face may not show it clearly.
Polishing: changing the surface pattern
In Make:’s final stage, polishing smooths the blade and removes the visible curl, leaving more aligned marks. This describes what appears in that particular image sequence; it does not guarantee the same result for every steel, edge geometry, abrasive, or sharpening technique.
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Why a burr can disappear from view
A burr is not simply a scratch. It is displaced metal at the very edge, and its appearance depends on which direction the edge is viewed from. In John D. Verhoeven’s 2004 technical report, Experiments on Knife Sharpening, one blade face appeared to have no significant burr, while the reverse face revealed a substantial one. The report says a fuller assessment uses images of both faces and an edge-on view to evaluate edge width.
That is why a single attractive close-up cannot establish that a burr is absent. ZWILLING’s care guidance likewise describes looking for a burr during stone sharpening, removing it, and checking the result by cutting paper. Those are manufacturer instructions for its context, not a universal specification for every knife.
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What an optical microscope can—and cannot—show
Magnification alone does not ensure a useful edge image. Verhoeven’s report notes that depth of field becomes very small at higher magnification; because a knife edge is curved, optical images lose usefulness much above “around 50x or so.” The report says scanning electron microscopy (SEM) has depth of field “on the order of 300 times better” and can provide clear knife-edge images at magnifications “up to 10,000x.” These are approximate figures from that 2004 report, not guarantees for every microscope or setup.
Lighting, focus, orientation, and the exact location photographed can all affect how an edge appears. A microscope can help inspect scratches and possible burrs, but an image is still a view of surface geometry—not a functional test.
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Do the images prove the knife became sharper?
No. The Make: demonstration documents visible changes to one edge, but it does not report a cutting-force test, standardized sharpness result, or edge-life comparison. A visual change may be consistent with sharpening, but it cannot quantify how much easier the knife cuts or how long the edge will last.
A separate commercial case article published by Tokushu Knife on August 1, 2026, shows microscopy of sampled VG10 and SG2/MC63 edges before and after stropping. Knife Edge Lab says the images show a cleaner-looking apex after a 2-micron stage and altered scratch patterns. Tokushu disclosed that it requested the microscopy and supplied the compound; the article says the work was not an accredited laboratory study, standardized sharpness test, or peer-reviewed research, and did not measure sharpness, bite, cutting force, or edge retention. Its photographed fields were not registered to identical microscopic locations at each stage, and the later 0.5–1 micron stage followed the 2-micron stage rather than serving as an independent head-to-head comparison. The observations are therefore a disclosed commercial case, not independent proof of product performance.
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Scan for outdated or missing drivers - takes under a minuteDriver Scan →Clear out junk files and repair common Windows errorsFree Scan →Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →To establish cutting performance or edge life, a comparison needs a defined cutting or force-test method. The microscope sequences described here do not provide that evidence.
Quick Recap
Sources and further reading
- Make:, Caleb Kraft, “See What Happens When You Sharpen a Knife Under a Microscope” (December 4, 2015)
- ZWILLING, “How To Sharpen Your Knives”
- John D. Verhoeven, Experiments on Knife Sharpening (2004)
- Knife Edge Lab / Tokushu Knife, “What Microscopy Shows After Stropping VG10 and SG2 Kitchen Knives” (August 1, 2026)
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