knifeopedia
Edge Maintenance
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Against popular belief, if a previously sharp knife starts feeling dull, it usually doesn't need to be sharpened. In most cases, the sharpness can be restored easily, and we will explain why and how.
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Imagine cutting a really hard pumpkin with a 24 cm Chef’s knife that has a super sharp cutting edge with AEB-L at HRC 62, sharpened to a very thin included angle of 15°. To get through that pumpkin, you have to use quite some pressure, so that chances are that you will hit the cutting board hard, which may cause the edge to roll. If so, the super sharpness that you were so proud of would be gone.
That doesn’t mean that you need to start sharpening all over again. The edge is not worn, it’s just bent as you can see in the picture. So all you need to do to restore the sharpness is to realign the edge to its proper angle.
There are different methods. The literature on- and offline refers to honing and stropping, but it can be confusing to understand the differences. Let's try to shed some light on this.
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Stropping in the original sense is a process to further refine/smoothen the edge after sharpening, removing residues, burs and scratches from the edge and giving it a polish. But stropping can also straighten/realign the edge.
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Honing by name also implies a refining of the cutting edge. But since it's usually done with honing rods, it does little to improve the edge of a newly and nicely sharpened knife. The main purpose of using a honing rod is to straighten/realign the edge and restore the sharpness of the knife. But depending on the coarseness of the rod, it will take material off the edge and thus sharpen the knife.
Since we talked about strops and honing rods in the context of sharpening already, we'll now explain how to straighten an edge.
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Straightening
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There are various tools that can be used for straightening/realigning a bent edge:
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Stropping block:
usually a strip of leather attached to a hard, flat base
Newspaper:
at least 10 pages of a newspaper put flat on a table
High grit whetstone:
3000 grit and above
Honing rod:
with very smooth or no ridges
With all of the above straightening tools, you need to PULL (important; not pushing!) the knife across the straightening medium with some pressure at roughly the same angle than your cutting edge, starting with a few pulls from each side, gradually reducing the number of pulls per side and easing up on the pressure towards the end. If done properly, you will see your original sharpness being restored rather quickly.
Microbevelling
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We already learnt that thin edges are more prone to chipping and rolling. Even hard steel, when taken to an acute angle, may roll when hitting a hard cutting board (e.g. bamboo) with some force. But there is a way to avoid this - adding a microbevel.
A microbevel is a second bevel on the very tip of your cutting edge at a wider angle, thus strengthening that super thin edge only at a micro-level. In cutting performance tests, this may result in a slight reduction of initial sharpness, but for the benefit of a considerably longer lasting sharpness of the edge.
In sharpening, a microbevel is produced on the finest grit of your sharpening device, with a few swipes from each side at a raised angle. So if you have sharpened your edge to an included angle of around 20°, the microbevel should be around 30°.
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Here a link to a good video, explaining how to apply a microlevel:
Grinding a microbevel on a new knife
In the knife community, microbevels are discussed controversially, also because the effect of them vary with steel, edge geometry and sharpening technique. However, if you feel that after sharpening, you have produced a super-sharp edge, but you are unhappy that the sharpness will be lost after just a day or two of cutting, try a microbevel.
Moreover, adding a microlevel can be recommended when the edge becomes chippy if taken to acute angles, which can be an issues if the blade is made of steel with a high carbide volume or large primary carbides.